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	$128.53	6.414%	$136.7739	$136.77	$136.75	$136.80
Purchase #2	$55.27	12.466%	$62.16	$62.16	$62.15	$62.20
Purchase #3	$116.41	13.121%	$131.6842	$131.68	$131.70	$131.70
Purchase #4	$180.52	3.813%	$187.4032	$187.40	$187.40	$187.40
Purchase #5	$42.41	9.625%	$46.492	$46.49	$46.50	$46.50
Purchase #6	$228.98	9.613%	$250.9918	$250.99	$251.00	$251.00
Purchase #7	$216.26	13.627%	$245.7298	$245.73	$245.75	$245.70
7 purchase totals =	$968.38		$1,061.2349	$1,061.22	$1,061.25	$1,061.30