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	$68.56	12.693%	$77.2623	$77.26	$77.25	$77.30
Purchase #2	$168.52	9.715%	$184.8917	$184.89	$184.90	$184.90
Purchase #3	$90.84	10.237%	$100.1393	$100.14	$100.15	$100.10
Purchase #4	$170.39	6.293%	$181.1126	$181.11	$181.10	$181.10
Purchase #5	$199.68	12.782%	$225.2031	$225.20	$225.20	$225.20
Purchase #6	$211.59	10.145%	$233.0558	$233.06	$233.05	$233.10
Purchase #7	$56.71	8.539%	$61.5525	$61.55	$61.55	$61.60
7 purchase totals =	$966.29		$1,063.2173	$1,063.21	$1,063.20	$1,063.30