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	$31.77	4.773%	$33.2864	$33.29	$33.30	$33.30
Purchase #2	$162.83	13.716%	$185.1638	$185.16	$185.15	$185.20
Purchase #3	$79.55	13.476%	$90.2702	$90.27	$90.25	$90.30
Purchase #4	$104.33	8.266%	$112.9539	$112.95	$112.95	$113.00
Purchase #5	$137.86	6.269%	$146.5024	$146.50	$146.50	$146.50
Purchase #6	$140.84	11.677%	$157.2859	$157.29	$157.30	$157.30
Purchase #7	$109.51	7.688%	$117.9291	$117.93	$117.95	$117.90
7 purchase totals =	$766.69		$843.3917	$843.39	$843.40	$843.50