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	$172.96	12.380%	$194.3724	$194.37	$194.35	$194.40
Purchase #2	$41.86	8.747%	$45.5215	$45.52	$45.50	$45.50
Purchase #3	$53.69	7.598%	$57.7694	$57.77	$57.75	$57.80
Purchase #4	$142.87	7.164%	$153.1052	$153.11	$153.10	$153.10
Purchase #5	$128.69	9.195%	$140.523	$140.52	$140.50	$140.50
Purchase #6	$104.77	12.722%	$118.0988	$118.10	$118.10	$118.10
Purchase #7	$121.67	5.164%	$127.953	$127.95	$127.95	$128.00
7 purchase totals =	$766.51		$837.3433	$837.34	$837.25	$837.40