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	$221.56	10.357%	$244.507	$244.51	$244.50	$244.50
Purchase #2	$124.97	5.258%	$131.5409	$131.54	$131.55	$131.50
Purchase #3	$117.58	11.547%	$131.157	$131.16	$131.15	$131.20
Purchase #4	$105.52	3.600%	$109.3187	$109.32	$109.30	$109.30
Purchase #5	$167.68	6.825%	$179.1242	$179.12	$179.10	$179.10
Purchase #6	$13.79	4.510%	$14.4119	$14.41	$14.40	$14.40
Purchase #7	$153.77	11.813%	$171.9349	$171.93	$171.95	$171.90
7 purchase totals =	$904.87		$981.9946	$981.99	$981.95	$981.90