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	$20.34	9.425%	$22.257	$22.26	$22.25	$22.30
Purchase #2	$148.55	6.670%	$158.4583	$158.46	$158.45	$158.50
Purchase #3	$250.94	13.708%	$285.3389	$285.34	$285.35	$285.30
Purchase #4	$199.54	11.666%	$222.8183	$222.82	$222.80	$222.80
Purchase #5	$51.54	12.275%	$57.8665	$57.87	$57.85	$57.90
Purchase #6	$185.29	8.453%	$200.9526	$200.95	$200.95	$201.00
Purchase #7	$96.85	3.373%	$100.1168	$100.12	$100.10	$100.10
7 purchase totals =	$953.05		$1,047.8084	$1,047.82	$1,047.75	$1,047.90