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	$144.44	6.461%	$153.7723	$153.77	$153.75	$153.80
Purchase #2	$50.53	7.192%	$54.1641	$54.16	$54.15	$54.20
Purchase #3	$181.42	7.168%	$194.4242	$194.42	$194.40	$194.40
Purchase #4	$57.70	8.316%	$62.4983	$62.50	$62.50	$62.50
Purchase #5	$74.51	10.790%	$82.5496	$82.55	$82.55	$82.50
Purchase #6	$226.98	8.102%	$245.3699	$245.37	$245.35	$245.40
Purchase #7	$126.89	3.487%	$131.3147	$131.31	$131.30	$131.30
7 purchase totals =	$862.47		$924.0931	$924.08	$924.00	$924.10