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	$209.90	12.697%	$236.551	$236.55	$236.55	$236.60
Purchase #2	$61.71	5.168%	$64.8992	$64.90	$64.90	$64.90
Purchase #3	$54.30	12.450%	$61.0604	$61.06	$61.05	$61.10
Purchase #4	$98.87	10.462%	$109.2138	$109.21	$109.20	$109.20
Purchase #5	$80.74	3.811%	$83.817	$83.82	$83.80	$83.80
Purchase #6	$93.68	7.510%	$100.7154	$100.72	$100.70	$100.70
Purchase #7	$85.57	11.286%	$95.2274	$95.23	$95.25	$95.20
7 purchase totals =	$684.77		$751.4842	$751.49	$751.45	$751.50