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	$12.86	4.344%	$13.4186	$13.42	$13.40	$13.40
Purchase #2	$172.60	13.619%	$196.1064	$196.11	$196.10	$196.10
Purchase #3	$211.31	5.105%	$222.0974	$222.10	$222.10	$222.10
Purchase #4	$230.59	4.386%	$240.7037	$240.70	$240.70	$240.70
Purchase #5	$216.94	8.591%	$235.5773	$235.58	$235.60	$235.60
Purchase #6	$209.54	6.788%	$223.7636	$223.76	$223.75	$223.80
Purchase #7	$39.46	13.465%	$44.7733	$44.77	$44.75	$44.80
7 purchase totals =	$1,093.30		$1,176.4403	$1,176.44	$1,176.40	$1,176.50