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	$69.29	10.597%	$76.6327	$76.63	$76.65	$76.60
Purchase #2	$206.41	5.685%	$218.1444	$218.14	$218.15	$218.10
Purchase #3	$67.94	6.676%	$72.4757	$72.48	$72.50	$72.50
Purchase #4	$74.85	11.403%	$83.3851	$83.39	$83.40	$83.40
Purchase #5	$212.89	13.801%	$242.2709	$242.27	$242.25	$242.30
Purchase #6	$102.73	7.573%	$110.5097	$110.51	$110.50	$110.50
Purchase #7	$120.74	12.218%	$135.492	$135.49	$135.50	$135.50
7 purchase totals =	$854.85		$938.9105	$938.91	$938.95	$938.90