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	$233.42	3.641%	$241.9188	$241.92	$241.90	$241.90
Purchase #2	$168.89	13.621%	$191.8945	$191.89	$191.90	$191.90
Purchase #3	$114.69	12.216%	$128.7005	$128.70	$128.70	$128.70
Purchase #4	$99.44	10.299%	$109.6813	$109.68	$109.70	$109.70
Purchase #5	$26.96	6.698%	$28.7658	$28.77	$28.75	$28.80
Purchase #6	$13.97	12.519%	$15.7189	$15.72	$15.70	$15.70
Purchase #7	$68.30	5.117%	$71.7949	$71.79	$71.80	$71.80
7 purchase totals =	$725.67		$788.4747	$788.47	$788.45	$788.50