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	$86.88	4.152%	$90.4873	$90.49	$90.50	$90.50
Purchase #2	$85.86	11.257%	$95.5253	$95.53	$95.55	$95.50
Purchase #3	$93.75	9.352%	$102.5175	$102.52	$102.50	$102.50
Purchase #4	$69.44	6.413%	$73.8932	$73.89	$73.90	$73.90
Purchase #5	$140.65	12.155%	$157.746	$157.75	$157.75	$157.70
Purchase #6	$250.38	9.863%	$275.075	$275.08	$275.10	$275.10
Purchase #7	$199.77	12.280%	$224.3018	$224.30	$224.30	$224.30
7 purchase totals =	$926.73		$1,019.5461	$1,019.56	$1,019.60	$1,019.50