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	$42.63	11.742%	$47.6356	$47.64	$47.65	$47.60
Purchase #2	$170.32	12.696%	$191.9438	$191.94	$191.95	$191.90
Purchase #3	$31.29	10.787%	$34.6653	$34.67	$34.65	$34.70
Purchase #4	$96.28	3.598%	$99.7442	$99.74	$99.75	$99.70
Purchase #5	$214.86	3.269%	$221.8838	$221.88	$221.90	$221.90
Purchase #6	$9.59	11.445%	$10.6876	$10.69	$10.70	$10.70
Purchase #7	$144.67	4.692%	$151.4579	$151.46	$151.45	$151.50
7 purchase totals =	$709.64		$758.0182	$758.02	$758.05	$758.00