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	$163.97	7.276%	$175.9005	$175.90	$175.90	$175.90
Purchase #2	$64.28	4.333%	$67.0653	$67.07	$67.05	$67.10
Purchase #3	$115.26	13.232%	$130.5112	$130.51	$130.50	$130.50
Purchase #4	$56.71	6.372%	$60.3236	$60.32	$60.30	$60.30
Purchase #5	$171.38	7.871%	$184.8693	$184.87	$184.85	$184.90
Purchase #6	$146.67	12.402%	$164.86	$164.86	$164.85	$164.90
Purchase #7	$237.46	10.716%	$262.9062	$262.91	$262.90	$262.90
7 purchase totals =	$955.73		$1,046.4361	$1,046.44	$1,046.35	$1,046.50