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	$62.92	13.564%	$71.4545	$71.45	$71.45	$71.50
Purchase #2	$191.61	7.576%	$206.1264	$206.13	$206.15	$206.10
Purchase #3	$219.85	4.289%	$229.2794	$229.28	$229.30	$229.30
Purchase #4	$47.88	4.511%	$50.0399	$50.04	$50.05	$50.00
Purchase #5	$6.37	8.751%	$6.9274	$6.93	$6.95	$6.90
Purchase #6	$53.69	10.144%	$59.1363	$59.14	$59.15	$59.10
Purchase #7	$220.83	13.494%	$250.6288	$250.63	$250.65	$250.60
7 purchase totals =	$803.15		$873.5927	$873.60	$873.70	$873.50