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	$47.82	13.183%	$54.1241	$54.12	$54.10	$54.10
Purchase #2	$48.32	3.769%	$50.1412	$50.14	$50.15	$50.10
Purchase #3	$188.37	3.111%	$194.2302	$194.23	$194.25	$194.20
Purchase #4	$182.55	7.641%	$196.4986	$196.50	$196.50	$196.50
Purchase #5	$90.63	13.390%	$102.7654	$102.77	$102.75	$102.80
Purchase #6	$55.72	12.859%	$62.885	$62.89	$62.90	$62.90
Purchase #7	$93.74	12.714%	$105.6581	$105.66	$105.65	$105.70
7 purchase totals =	$707.15		$766.3026	$766.31	$766.30	$766.30