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	$117.36	10.567%	$129.7614	$129.76	$129.75	$129.80
Purchase #2	$137.77	7.620%	$148.2681	$148.27	$148.25	$148.30
Purchase #3	$71.89	10.377%	$79.35	$79.35	$79.35	$79.40
Purchase #4	$200.56	9.459%	$219.531	$219.53	$219.55	$219.50
Purchase #5	$245.50	3.392%	$253.8274	$253.83	$253.85	$253.80
Purchase #6	$103.85	7.216%	$111.3438	$111.34	$111.35	$111.30
Purchase #7	$228.74	12.817%	$258.0576	$258.06	$258.05	$258.10
7 purchase totals =	$1,105.67		$1,200.1393	$1,200.14	$1,200.15	$1,200.20