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	$17.25	5.143%	$18.1372	$18.14	$18.15	$18.10
Purchase #2	$191.94	10.761%	$212.5947	$212.59	$212.60	$212.60
Purchase #3	$127.84	13.516%	$145.1189	$145.12	$145.10	$145.10
Purchase #4	$99.31	12.628%	$111.8509	$111.85	$111.85	$111.90
Purchase #5	$108.79	8.571%	$118.1144	$118.11	$118.10	$118.10
Purchase #6	$62.87	10.234%	$69.3041	$69.30	$69.30	$69.30
Purchase #7	$189.72	10.624%	$209.8759	$209.88	$209.90	$209.90
7 purchase totals =	$797.72		$884.9961	$884.99	$885.00	$885.00