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	$162.27	11.205%	$180.4524	$180.45	$180.45	$180.50
Purchase #2	$130.60	7.553%	$140.4642	$140.46	$140.45	$140.50
Purchase #3	$147.39	12.500%	$165.8138	$165.81	$165.80	$165.80
Purchase #4	$28.46	13.543%	$32.3143	$32.31	$32.30	$32.30
Purchase #5	$54.54	12.541%	$61.3799	$61.38	$61.40	$61.40
Purchase #6	$191.59	5.358%	$201.8554	$201.86	$201.85	$201.90
Purchase #7	$185.27	7.334%	$198.8577	$198.86	$198.85	$198.90
7 purchase totals =	$900.12		$981.1377	$981.13	$981.10	$981.30