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	$93.74	11.505%	$104.5248	$104.52	$104.50	$104.50
Purchase #2	$214.70	11.370%	$239.1114	$239.11	$239.10	$239.10
Purchase #3	$226.30	4.497%	$236.4767	$236.48	$236.50	$236.50
Purchase #4	$134.36	7.251%	$144.1024	$144.10	$144.10	$144.10
Purchase #5	$183.66	7.856%	$198.0883	$198.09	$198.10	$198.10
Purchase #6	$120.34	5.778%	$127.2932	$127.29	$127.30	$127.30
Purchase #7	$119.74	3.467%	$123.8914	$123.89	$123.90	$123.90
7 purchase totals =	$1,092.84		$1,173.4882	$1,173.48	$1,173.50	$1,173.50