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	$210.95	10.871%	$233.8824	$233.88	$233.90	$233.90
Purchase #2	$123.56	12.523%	$139.0334	$139.03	$139.05	$139.00
Purchase #3	$115.58	3.668%	$119.8195	$119.82	$119.80	$119.80
Purchase #4	$153.91	3.696%	$159.5985	$159.60	$159.60	$159.60
Purchase #5	$101.51	9.112%	$110.7596	$110.76	$110.75	$110.80
Purchase #6	$249.72	7.465%	$268.3616	$268.36	$268.35	$268.40
Purchase #7	$89.52	12.482%	$100.6939	$100.69	$100.70	$100.70
7 purchase totals =	$1,044.75		$1,132.1489	$1,132.14	$1,132.15	$1,132.20