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	$213.79	10.575%	$236.3983	$236.40	$236.40	$236.40
Purchase #2	$100.72	7.477%	$108.2508	$108.25	$108.25	$108.30
Purchase #3	$246.33	12.609%	$277.3897	$277.39	$277.40	$277.40
Purchase #4	$68.49	12.589%	$77.1122	$77.11	$77.10	$77.10
Purchase #5	$59.78	9.452%	$65.4304	$65.43	$65.45	$65.40
Purchase #6	$61.58	4.564%	$64.3905	$64.39	$64.40	$64.40
Purchase #7	$143.59	6.180%	$152.4639	$152.46	$152.45	$152.50
7 purchase totals =	$894.28		$981.4358	$981.43	$981.45	$981.50