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	$73.57	12.280%	$82.6044	$82.60	$82.60	$82.60
Purchase #2	$95.93	4.404%	$100.1548	$100.15	$100.15	$100.20
Purchase #3	$159.58	4.355%	$166.5297	$166.53	$166.55	$166.50
Purchase #4	$178.84	11.304%	$199.0561	$199.06	$199.05	$199.10
Purchase #5	$104.28	5.749%	$110.2751	$110.28	$110.30	$110.30
Purchase #6	$79.77	4.533%	$83.386	$83.39	$83.40	$83.40
Purchase #7	$156.76	13.403%	$177.7705	$177.77	$177.75	$177.80
7 purchase totals =	$848.73		$919.7766	$919.78	$919.80	$919.90