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	$155.66	7.578%	$167.4559	$167.46	$167.45	$167.50
Purchase #2	$243.30	13.139%	$275.2672	$275.27	$275.25	$275.30
Purchase #3	$237.66	4.747%	$248.9417	$248.94	$248.95	$248.90
Purchase #4	$32.36	9.498%	$35.4336	$35.43	$35.45	$35.40
Purchase #5	$130.76	12.234%	$146.7572	$146.76	$146.75	$146.80
Purchase #6	$58.67	6.583%	$62.5322	$62.53	$62.55	$62.50
Purchase #7	$99.60	9.867%	$109.4275	$109.43	$109.45	$109.40
7 purchase totals =	$958.01		$1,045.8153	$1,045.82	$1,045.85	$1,045.80