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	$94.55	11.465%	$105.3902	$105.39	$105.40	$105.40
Purchase #2	$59.78	5.287%	$62.9406	$62.94	$62.95	$62.90
Purchase #3	$227.89	11.199%	$253.4114	$253.41	$253.40	$253.40
Purchase #4	$42.33	13.170%	$47.9049	$47.90	$47.90	$47.90
Purchase #5	$250.43	8.385%	$271.4286	$271.43	$271.45	$271.40
Purchase #6	$83.32	11.796%	$93.1484	$93.15	$93.15	$93.10
Purchase #7	$93.40	9.799%	$102.5523	$102.55	$102.55	$102.60
7 purchase totals =	$851.70		$936.7764	$936.77	$936.80	$936.70