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	$195.86	13.252%	$221.8154	$221.82	$221.80	$221.80
Purchase #2	$155.52	10.391%	$171.6801	$171.68	$171.70	$171.70
Purchase #3	$72.98	12.805%	$82.3251	$82.33	$82.35	$82.30
Purchase #4	$170.26	7.590%	$183.1827	$183.18	$183.20	$183.20
Purchase #5	$246.69	11.663%	$275.4615	$275.46	$275.45	$275.50
Purchase #6	$175.64	12.127%	$196.9399	$196.94	$196.95	$196.90
Purchase #7	$135.65	9.331%	$148.3075	$148.31	$148.30	$148.30
7 purchase totals =	$1,152.60		$1,279.7122	$1,279.72	$1,279.75	$1,279.70