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	$146.72	5.719%	$155.1109	$155.11	$155.10	$155.10
Purchase #2	$10.90	12.239%	$12.2341	$12.23	$12.25	$12.20
Purchase #3	$32.57	9.824%	$35.7697	$35.77	$35.75	$35.80
Purchase #4	$186.50	7.524%	$200.5323	$200.53	$200.55	$200.50
Purchase #5	$183.39	4.304%	$191.2831	$191.28	$191.30	$191.30
Purchase #6	$74.99	6.122%	$79.5809	$79.58	$79.60	$79.60
Purchase #7	$89.52	3.665%	$92.8009	$92.80	$92.80	$92.80
7 purchase totals =	$724.59		$767.3119	$767.30	$767.35	$767.30