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	$52.60	12.783%	$59.3239	$59.32	$59.30	$59.30
Purchase #2	$59.81	12.541%	$67.3108	$67.31	$67.30	$67.30
Purchase #3	$64.60	10.184%	$71.1789	$71.18	$71.20	$71.20
Purchase #4	$94.83	11.663%	$105.89	$105.89	$105.90	$105.90
Purchase #5	$160.71	6.446%	$171.0694	$171.07	$171.05	$171.10
Purchase #6	$111.65	13.259%	$126.4537	$126.45	$126.45	$126.50
Purchase #7	$152.64	6.403%	$162.4135	$162.41	$162.40	$162.40
7 purchase totals =	$696.84		$763.6402	$763.63	$763.60	$763.70