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	$59.96	7.250%	$64.3071	$64.31	$64.30	$64.30
Purchase #2	$166.59	4.670%	$174.3698	$174.37	$174.35	$174.40
Purchase #3	$230.38	6.491%	$245.334	$245.33	$245.35	$245.30
Purchase #4	$99.99	11.373%	$111.3619	$111.36	$111.35	$111.40
Purchase #5	$87.28	4.584%	$91.2809	$91.28	$91.30	$91.30
Purchase #6	$127.32	7.487%	$136.8524	$136.85	$136.85	$136.90
Purchase #7	$231.57	6.689%	$247.0597	$247.06	$247.05	$247.10
7 purchase totals =	$1,003.09		$1,070.5658	$1,070.56	$1,070.55	$1,070.70