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	$223.32	6.717%	$238.3204	$238.32	$238.30	$238.30
Purchase #2	$193.93	8.516%	$210.4451	$210.45	$210.45	$210.40
Purchase #3	$113.69	5.263%	$119.6735	$119.67	$119.65	$119.70
Purchase #4	$199.26	6.799%	$212.8077	$212.81	$212.80	$212.80
Purchase #5	$145.38	4.186%	$151.4656	$151.47	$151.45	$151.50
Purchase #6	$33.47	12.727%	$37.7297	$37.73	$37.75	$37.70
Purchase #7	$170.55	12.826%	$192.4247	$192.42	$192.40	$192.40
7 purchase totals =	$1,079.60		$1,162.8667	$1,162.87	$1,162.80	$1,162.80