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	$98.67	12.389%	$110.8942	$110.89	$110.90	$110.90
Purchase #2	$105.63	8.370%	$114.4712	$114.47	$114.45	$114.50
Purchase #3	$18.48	12.131%	$20.7218	$20.72	$20.70	$20.70
Purchase #4	$250.28	8.626%	$271.8692	$271.87	$271.85	$271.90
Purchase #5	$234.88	3.385%	$242.8307	$242.83	$242.85	$242.80
Purchase #6	$214.59	13.458%	$243.4695	$243.47	$243.45	$243.50
Purchase #7	$167.97	13.585%	$190.7887	$190.79	$190.80	$190.80
7 purchase totals =	$1,090.50		$1,195.0453	$1,195.04	$1,195.00	$1,195.10