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	$134.25	12.294%	$150.7547	$150.75	$150.75	$150.80
Purchase #2	$52.89	7.404%	$56.806	$56.81	$56.80	$56.80
Purchase #3	$171.88	11.314%	$191.3265	$191.33	$191.35	$191.30
Purchase #4	$200.92	8.569%	$218.1368	$218.14	$218.15	$218.10
Purchase #5	$21.58	8.501%	$23.4145	$23.41	$23.40	$23.40
Purchase #6	$205.98	3.149%	$212.4663	$212.47	$212.45	$212.50
Purchase #7	$103.54	5.282%	$109.009	$109.01	$109.00	$109.00
7 purchase totals =	$891.04		$961.9138	$961.92	$961.90	$961.90