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	$75.89	4.714%	$79.4675	$79.47	$79.45	$79.50
Purchase #2	$208.61	9.800%	$229.0538	$229.05	$229.05	$229.10
Purchase #3	$137.73	10.281%	$151.89	$151.89	$151.90	$151.90
Purchase #4	$54.81	3.236%	$56.5837	$56.58	$56.60	$56.60
Purchase #5	$249.79	3.660%	$258.9323	$258.93	$258.95	$258.90
Purchase #6	$170.67	7.259%	$183.0589	$183.06	$183.05	$183.10
Purchase #7	$187.80	13.380%	$212.9276	$212.93	$212.95	$212.90
7 purchase totals =	$1,085.30		$1,171.9138	$1,171.91	$1,171.95	$1,172.00