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	$157.63	13.757%	$179.3152	$179.32	$179.30	$179.30
Purchase #2	$162.81	13.801%	$185.2794	$185.28	$185.30	$185.30
Purchase #3	$98.83	11.579%	$110.2735	$110.27	$110.25	$110.30
Purchase #4	$114.85	11.656%	$128.2369	$128.24	$128.25	$128.20
Purchase #5	$198.36	12.494%	$223.1431	$223.14	$223.15	$223.10
Purchase #6	$160.69	13.176%	$181.8625	$181.86	$181.85	$181.90
Purchase #7	$33.42	10.816%	$37.0347	$37.03	$37.05	$37.00
7 purchase totals =	$926.59		$1,045.1453	$1,045.14	$1,045.15	$1,045.10