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	$67.53	5.741%	$71.4069	$71.41	$71.40	$71.40
Purchase #2	$216.48	6.360%	$230.2481	$230.25	$230.25	$230.20
Purchase #3	$131.41	9.566%	$143.9807	$143.98	$144.00	$144.00
Purchase #4	$111.58	10.820%	$123.653	$123.65	$123.65	$123.70
Purchase #5	$180.43	10.789%	$199.8966	$199.90	$199.90	$199.90
Purchase #6	$149.45	8.754%	$162.5329	$162.53	$162.55	$162.50
Purchase #7	$111.63	3.377%	$115.3997	$115.40	$115.40	$115.40
7 purchase totals =	$968.51		$1,047.1179	$1,047.12	$1,047.15	$1,047.10