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	$156.34	3.484%	$161.7869	$161.79	$161.80	$161.80
Purchase #2	$177.55	12.423%	$199.607	$199.61	$199.60	$199.60
Purchase #3	$36.33	6.601%	$38.7281	$38.73	$38.75	$38.70
Purchase #4	$178.52	6.592%	$190.288	$190.29	$190.30	$190.30
Purchase #5	$77.71	12.333%	$87.294	$87.29	$87.30	$87.30
Purchase #6	$152.63	12.410%	$171.5714	$171.57	$171.55	$171.60
Purchase #7	$146.34	5.398%	$154.2394	$154.24	$154.25	$154.20
7 purchase totals =	$925.42		$1,003.5148	$1,003.52	$1,003.55	$1,003.50