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	$59.61	4.498%	$62.2913	$62.29	$62.30	$62.30
Purchase #2	$229.83	3.360%	$237.5523	$237.55	$237.55	$237.60
Purchase #3	$82.76	10.141%	$91.1527	$91.15	$91.15	$91.20
Purchase #4	$143.86	6.154%	$152.7131	$152.71	$152.70	$152.70
Purchase #5	$114.70	7.813%	$123.6615	$123.66	$123.65	$123.70
Purchase #6	$174.90	13.634%	$198.7459	$198.75	$198.75	$198.70
Purchase #7	$29.82	8.543%	$32.3675	$32.37	$32.35	$32.40
7 purchase totals =	$835.48		$898.4843	$898.48	$898.45	$898.60