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	$175.87	5.601%	$185.7205	$185.72	$185.70	$185.70
Purchase #2	$9.59	9.716%	$10.5218	$10.52	$10.50	$10.50
Purchase #3	$123.61	10.598%	$136.7102	$136.71	$136.70	$136.70
Purchase #4	$222.57	7.809%	$239.9505	$239.95	$239.95	$240.00
Purchase #5	$188.33	6.369%	$200.3247	$200.32	$200.30	$200.30
Purchase #6	$168.68	3.815%	$175.1151	$175.12	$175.10	$175.10
Purchase #7	$29.56	9.308%	$32.3114	$32.31	$32.30	$32.30
7 purchase totals =	$918.21		$980.6542	$980.65	$980.55	$980.60