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	$171.27	7.748%	$184.54	$184.54	$184.55	$184.50
Purchase #2	$36.29	9.771%	$39.8359	$39.84	$39.85	$39.80
Purchase #3	$107.98	3.642%	$111.9126	$111.91	$111.90	$111.90
Purchase #4	$55.69	7.846%	$60.0594	$60.06	$60.05	$60.10
Purchase #5	$116.97	5.347%	$123.2244	$123.22	$123.20	$123.20
Purchase #6	$101.48	11.540%	$113.1908	$113.19	$113.20	$113.20
Purchase #7	$240.63	6.440%	$256.1266	$256.13	$256.15	$256.10
7 purchase totals =	$830.31		$888.8897	$888.89	$888.90	$888.80