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	$92.68	7.847%	$99.9526	$99.95	$99.95	$100.00
Purchase #2	$118.33	8.690%	$128.6129	$128.61	$128.60	$128.60
Purchase #3	$123.95	6.227%	$131.6684	$131.67	$131.65	$131.70
Purchase #4	$30.44	5.342%	$32.0661	$32.07	$32.05	$32.10
Purchase #5	$237.41	12.781%	$267.7534	$267.75	$267.75	$267.80
Purchase #6	$143.64	8.557%	$155.9313	$155.93	$155.95	$155.90
Purchase #7	$229.46	11.593%	$256.0613	$256.06	$256.05	$256.10
7 purchase totals =	$975.91		$1,072.0460	$1,072.04	$1,072.00	$1,072.20