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	$200.77	13.605%	$228.0848	$228.08	$228.10	$228.10
Purchase #2	$52.89	5.378%	$55.7344	$55.73	$55.75	$55.70
Purchase #3	$94.61	5.145%	$99.4777	$99.48	$99.50	$99.50
Purchase #4	$188.90	13.757%	$214.887	$214.89	$214.90	$214.90
Purchase #5	$36.34	6.276%	$38.6207	$38.62	$38.60	$38.60
Purchase #6	$24.47	12.542%	$27.539	$27.54	$27.55	$27.50
Purchase #7	$58.46	13.589%	$66.4041	$66.40	$66.40	$66.40
7 purchase totals =	$656.44		$730.7477	$730.74	$730.80	$730.70