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	$229.67	5.791%	$242.9702	$242.97	$242.95	$243.00
Purchase #2	$86.66	10.678%	$95.9136	$95.91	$95.90	$95.90
Purchase #3	$33.95	13.182%	$38.4253	$38.43	$38.45	$38.40
Purchase #4	$40.84	11.612%	$45.5823	$45.58	$45.60	$45.60
Purchase #5	$103.94	10.809%	$115.1749	$115.17	$115.15	$115.20
Purchase #6	$250.83	5.632%	$264.9567	$264.96	$264.95	$265.00
Purchase #7	$196.61	10.152%	$216.5698	$216.57	$216.55	$216.60
7 purchase totals =	$942.50		$1,019.5928	$1,019.59	$1,019.55	$1,019.70