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	$167.81	13.449%	$190.3788	$190.38	$190.40	$190.40
Purchase #2	$238.32	6.813%	$254.5567	$254.56	$254.55	$254.60
Purchase #3	$151.48	13.466%	$171.8783	$171.88	$171.90	$171.90
Purchase #4	$104.42	7.103%	$111.837	$111.84	$111.85	$111.80
Purchase #5	$210.29	13.844%	$239.4025	$239.40	$239.40	$239.40
Purchase #6	$55.70	6.449%	$59.2921	$59.29	$59.30	$59.30
Purchase #7	$219.76	4.165%	$228.913	$228.91	$228.90	$228.90
7 purchase totals =	$1,147.78		$1,256.2584	$1,256.26	$1,256.30	$1,256.30