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	$171.33	7.643%	$184.4248	$184.42	$184.40	$184.40
Purchase #2	$123.33	11.394%	$137.3822	$137.38	$137.40	$137.40
Purchase #3	$105.35	3.656%	$109.2016	$109.20	$109.20	$109.20
Purchase #4	$161.72	6.511%	$172.2496	$172.25	$172.25	$172.20
Purchase #5	$224.79	11.270%	$250.1238	$250.12	$250.10	$250.10
Purchase #6	$62.57	8.185%	$67.6914	$67.69	$67.70	$67.70
Purchase #7	$152.27	7.588%	$163.8242	$163.82	$163.80	$163.80
7 purchase totals =	$1,001.36		$1,084.8976	$1,084.88	$1,084.85	$1,084.80