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	$151.65	5.360%	$159.7784	$159.78	$159.80	$159.80
Purchase #2	$127.88	7.748%	$137.7881	$137.79	$137.80	$137.80
Purchase #3	$122.41	5.185%	$128.757	$128.76	$128.75	$128.80
Purchase #4	$31.48	6.593%	$33.5555	$33.56	$33.55	$33.60
Purchase #5	$226.82	9.585%	$248.5607	$248.56	$248.55	$248.60
Purchase #6	$153.74	9.399%	$168.19	$168.19	$168.20	$168.20
Purchase #7	$119.67	6.830%	$127.8435	$127.84	$127.85	$127.80
7 purchase totals =	$933.65		$1,004.4732	$1,004.48	$1,004.50	$1,004.60