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	$136.34	11.801%	$152.4295	$152.43	$152.45	$152.40
Purchase #2	$179.94	13.571%	$204.3597	$204.36	$204.35	$204.40
Purchase #3	$33.79	11.540%	$37.6894	$37.69	$37.70	$37.70
Purchase #4	$202.75	3.859%	$210.5741	$210.57	$210.55	$210.60
Purchase #5	$150.49	12.758%	$169.6895	$169.69	$169.70	$169.70
Purchase #6	$178.39	10.340%	$196.8355	$196.84	$196.85	$196.80
Purchase #7	$229.64	4.573%	$240.1414	$240.14	$240.15	$240.10
7 purchase totals =	$1,111.34		$1,211.7191	$1,211.72	$1,211.75	$1,211.70