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	$155.50	6.695%	$165.9107	$165.91	$165.90	$165.90
Purchase #2	$85.60	8.542%	$92.912	$92.91	$92.90	$92.90
Purchase #3	$172.30	4.776%	$180.529	$180.53	$180.55	$180.50
Purchase #4	$88.39	12.137%	$99.1179	$99.12	$99.10	$99.10
Purchase #5	$232.26	7.105%	$248.7621	$248.76	$248.75	$248.80
Purchase #6	$213.94	10.172%	$235.702	$235.70	$235.70	$235.70
Purchase #7	$115.30	10.457%	$127.3569	$127.36	$127.35	$127.40
7 purchase totals =	$1,063.29		$1,150.2906	$1,150.29	$1,150.25	$1,150.30