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	$168.74	13.589%	$191.6701	$191.67	$191.65	$191.70
Purchase #2	$110.80	4.738%	$116.0497	$116.05	$116.05	$116.00
Purchase #3	$91.61	8.433%	$99.3355	$99.34	$99.35	$99.30
Purchase #4	$58.29	7.391%	$62.5982	$62.60	$62.60	$62.60
Purchase #5	$151.87	10.701%	$168.1216	$168.12	$168.10	$168.10
Purchase #6	$233.51	9.261%	$255.1354	$255.14	$255.15	$255.10
Purchase #7	$135.58	12.154%	$152.0584	$152.06	$152.05	$152.10
7 purchase totals =	$950.40		$1,044.9689	$1,044.98	$1,044.95	$1,044.90