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	$176.45	13.667%	$200.5654	$200.57	$200.55	$200.60
Purchase #2	$32.83	8.167%	$35.5112	$35.51	$35.50	$35.50
Purchase #3	$46.41	3.290%	$47.9369	$47.94	$47.95	$47.90
Purchase #4	$190.29	12.667%	$214.394	$214.39	$214.40	$214.40
Purchase #5	$249.86	9.156%	$272.7372	$272.74	$272.75	$272.70
Purchase #6	$188.45	11.641%	$210.3875	$210.39	$210.40	$210.40
Purchase #7	$58.33	11.267%	$64.902	$64.90	$64.90	$64.90
7 purchase totals =	$942.62		$1,046.4342	$1,046.44	$1,046.45	$1,046.40