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	$139.53	8.216%	$150.9938	$150.99	$151.00	$151.00
Purchase #2	$66.51	8.274%	$72.013	$72.01	$72.00	$72.00
Purchase #3	$185.45	8.173%	$200.6068	$200.61	$200.60	$200.60
Purchase #4	$249.45	11.561%	$278.2889	$278.29	$278.30	$278.30
Purchase #5	$245.97	3.740%	$255.1693	$255.17	$255.15	$255.20
Purchase #6	$179.47	8.102%	$194.0107	$194.01	$194.00	$194.00
Purchase #7	$143.62	3.774%	$149.0402	$149.04	$149.05	$149.00
7 purchase totals =	$1,210.00		$1,300.1227	$1,300.12	$1,300.10	$1,300.10