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	$233.45	6.546%	$248.7316	$248.73	$248.75	$248.70
Purchase #2	$78.78	9.225%	$86.0475	$86.05	$86.05	$86.00
Purchase #3	$40.45	11.713%	$45.1879	$45.19	$45.20	$45.20
Purchase #4	$146.54	8.817%	$159.4604	$159.46	$159.45	$159.50
Purchase #5	$178.42	3.758%	$185.125	$185.13	$185.15	$185.10
Purchase #6	$90.97	8.873%	$99.0418	$99.04	$99.05	$99.00
Purchase #7	$186.27	4.246%	$194.179	$194.18	$194.20	$194.20
7 purchase totals =	$954.88		$1,017.7732	$1,017.78	$1,017.85	$1,017.70