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	$136.30	10.685%	$150.8637	$150.86	$150.85	$150.90
Purchase #2	$13.98	9.679%	$15.3331	$15.33	$15.35	$15.30
Purchase #3	$233.73	12.661%	$263.3226	$263.32	$263.30	$263.30
Purchase #4	$185.39	11.459%	$206.6338	$206.63	$206.65	$206.60
Purchase #5	$201.37	4.374%	$210.1779	$210.18	$210.20	$210.20
Purchase #6	$92.71	7.371%	$99.5437	$99.54	$99.55	$99.50
Purchase #7	$122.49	3.686%	$127.005	$127.01	$127.00	$127.00
7 purchase totals =	$985.97		$1,072.8798	$1,072.87	$1,072.90	$1,072.80