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	$53.45	3.492%	$55.3165	$55.32	$55.30	$55.30
Purchase #2	$22.48	13.841%	$25.5915	$25.59	$25.60	$25.60
Purchase #3	$145.78	9.138%	$159.1014	$159.10	$159.10	$159.10
Purchase #4	$179.76	4.842%	$188.464	$188.46	$188.45	$188.50
Purchase #5	$32.94	8.192%	$35.6384	$35.64	$35.65	$35.60
Purchase #6	$30.82	7.636%	$33.1734	$33.17	$33.15	$33.20
Purchase #7	$108.73	13.513%	$123.4227	$123.42	$123.40	$123.40
7 purchase totals =	$573.96		$620.7079	$620.70	$620.65	$620.70