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	$220.93	5.514%	$233.1121	$233.11	$233.10	$233.10
Purchase #2	$140.28	10.595%	$155.1427	$155.14	$155.15	$155.10
Purchase #3	$53.48	10.600%	$59.1489	$59.15	$59.15	$59.10
Purchase #4	$103.98	4.601%	$108.7641	$108.76	$108.75	$108.80
Purchase #5	$134.91	3.171%	$139.188	$139.19	$139.20	$139.20
Purchase #6	$74.64	10.745%	$82.6601	$82.66	$82.65	$82.70
Purchase #7	$242.63	10.687%	$268.5599	$268.56	$268.55	$268.60
7 purchase totals =	$970.85		$1,046.5758	$1,046.57	$1,046.55	$1,046.60