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	$204.50	7.534%	$219.907	$219.91	$219.90	$219.90
Purchase #2	$138.47	3.226%	$142.937	$142.94	$142.95	$142.90
Purchase #3	$57.55	8.675%	$62.5425	$62.54	$62.55	$62.50
Purchase #4	$90.43	6.427%	$96.2419	$96.24	$96.25	$96.20
Purchase #5	$59.53	6.358%	$63.3149	$63.31	$63.30	$63.30
Purchase #6	$86.58	9.603%	$94.8943	$94.89	$94.90	$94.90
Purchase #7	$58.69	4.437%	$61.2941	$61.29	$61.30	$61.30
7 purchase totals =	$695.75		$741.1317	$741.12	$741.15	$741.00