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	$100.32	4.450%	$104.7842	$104.78	$104.80	$104.80
Purchase #2	$12.85	4.292%	$13.4015	$13.40	$13.40	$13.40
Purchase #3	$134.93	6.529%	$143.7396	$143.74	$143.75	$143.70
Purchase #4	$70.64	7.408%	$75.873	$75.87	$75.85	$75.90
Purchase #5	$35.33	11.323%	$39.3304	$39.33	$39.35	$39.30
Purchase #6	$88.83	13.479%	$100.8034	$100.80	$100.80	$100.80
Purchase #7	$166.65	11.296%	$185.4748	$185.47	$185.45	$185.50
7 purchase totals =	$609.55		$663.4069	$663.39	$663.40	$663.40