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	$120.92	8.760%	$131.5126	$131.51	$131.50	$131.50
Purchase #2	$12.65	10.109%	$13.9288	$13.93	$13.95	$13.90
Purchase #3	$238.58	12.384%	$268.1257	$268.13	$268.15	$268.10
Purchase #4	$108.65	5.169%	$114.2661	$114.27	$114.25	$114.30
Purchase #5	$189.52	12.828%	$213.8316	$213.83	$213.85	$213.80
Purchase #6	$238.97	4.840%	$250.5361	$250.54	$250.55	$250.50
Purchase #7	$35.72	13.858%	$40.6701	$40.67	$40.65	$40.70
7 purchase totals =	$945.01		$1,032.8710	$1,032.88	$1,032.90	$1,032.80