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	$228.46	4.232%	$238.1284	$238.13	$238.15	$238.10
Purchase #2	$20.99	3.531%	$21.7312	$21.73	$21.75	$21.70
Purchase #3	$50.98	3.206%	$52.6144	$52.61	$52.60	$52.60
Purchase #4	$62.87	7.796%	$67.7713	$67.77	$67.75	$67.80
Purchase #5	$182.88	12.114%	$205.0341	$205.03	$205.05	$205.00
Purchase #6	$16.69	9.798%	$18.3253	$18.33	$18.35	$18.30
Purchase #7	$214.83	3.760%	$222.9076	$222.91	$222.90	$222.90
7 purchase totals =	$777.70		$826.5123	$826.51	$826.55	$826.40