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	$238.59	3.721%	$247.4679	$247.47	$247.45	$247.50
Purchase #2	$17.27	3.420%	$17.8606	$17.86	$17.85	$17.90
Purchase #3	$196.95	11.385%	$219.3728	$219.37	$219.35	$219.40
Purchase #4	$90.46	11.523%	$100.8837	$100.88	$100.90	$100.90
Purchase #5	$23.99	4.573%	$25.0871	$25.09	$25.10	$25.10
Purchase #6	$64.33	13.476%	$72.9991	$73.00	$73.00	$73.00
Purchase #7	$99.59	11.335%	$110.8785	$110.88	$110.90	$110.90
7 purchase totals =	$731.18		$794.5497	$794.55	$794.55	$794.70