Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$214.84	8.685%	$233.4989	$233.50	$233.50	$233.50
Purchase #2	$162.49	11.423%	$181.0512	$181.05	$181.05	$181.10
Purchase #3	$213.31	10.246%	$235.1657	$235.17	$235.15	$235.20
Purchase #4	$207.50	12.374%	$233.1761	$233.18	$233.20	$233.20
Purchase #5	$93.39	12.763%	$105.3094	$105.31	$105.30	$105.30
Purchase #6	$91.74	12.153%	$102.8892	$102.89	$102.90	$102.90
Purchase #7	$144.78	10.172%	$159.507	$159.51	$159.50	$159.50
7 purchase totals =	$1,128.05		$1,250.5975	$1,250.61	$1,250.60	$1,250.70