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	$143.73	13.215%	$162.7239	$162.72	$162.70	$162.70
Purchase #2	$231.99	7.539%	$249.4797	$249.48	$249.50	$249.50
Purchase #3	$210.52	3.798%	$218.5155	$218.52	$218.50	$218.50
Purchase #4	$125.39	4.681%	$131.2595	$131.26	$131.25	$131.30
Purchase #5	$176.31	6.454%	$187.689	$187.69	$187.70	$187.70
Purchase #6	$230.58	10.376%	$254.505	$254.51	$254.50	$254.50
Purchase #7	$199.73	6.791%	$213.2937	$213.29	$213.30	$213.30
7 purchase totals =	$1,318.25		$1,417.4663	$1,417.47	$1,417.45	$1,417.50