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	$152.32	11.511%	$169.8536	$169.85	$169.85	$169.90
Purchase #2	$45.61	10.779%	$50.5263	$50.53	$50.55	$50.50
Purchase #3	$236.74	13.480%	$268.6526	$268.65	$268.65	$268.70
Purchase #4	$55.64	12.351%	$62.5121	$62.51	$62.50	$62.50
Purchase #5	$92.95	13.227%	$105.2445	$105.24	$105.25	$105.20
Purchase #6	$243.34	9.524%	$266.5157	$266.52	$266.50	$266.50
Purchase #7	$90.86	10.381%	$100.2922	$100.29	$100.30	$100.30
7 purchase totals =	$917.46		$1,023.5970	$1,023.59	$1,023.60	$1,023.60