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	$42.84	11.269%	$47.6676	$47.67	$47.65	$47.70
Purchase #2	$236.86	7.118%	$253.7197	$253.72	$253.70	$253.70
Purchase #3	$174.83	4.172%	$182.1239	$182.12	$182.10	$182.10
Purchase #4	$99.26	7.343%	$106.5487	$106.55	$106.55	$106.50
Purchase #5	$176.78	6.789%	$188.7816	$188.78	$188.80	$188.80
Purchase #6	$48.88	11.402%	$54.4533	$54.45	$54.45	$54.50
Purchase #7	$71.50	9.361%	$78.1931	$78.19	$78.20	$78.20
7 purchase totals =	$850.95		$911.4879	$911.48	$911.45	$911.50