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	$70.35	3.404%	$72.7447	$72.74	$72.75	$72.70
Purchase #2	$169.90	3.374%	$175.6324	$175.63	$175.65	$175.60
Purchase #3	$161.64	13.182%	$182.9474	$182.95	$182.95	$182.90
Purchase #4	$55.55	13.162%	$62.8615	$62.86	$62.85	$62.90
Purchase #5	$105.78	13.607%	$120.1735	$120.17	$120.15	$120.20
Purchase #6	$79.37	4.415%	$82.8742	$82.87	$82.85	$82.90
Purchase #7	$231.26	12.556%	$260.297	$260.30	$260.30	$260.30
7 purchase totals =	$873.85		$957.5307	$957.52	$957.50	$957.50