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	$181.73	6.303%	$193.1844	$193.18	$193.20	$193.20
Purchase #2	$185.66	3.184%	$191.5714	$191.57	$191.55	$191.60
Purchase #3	$148.48	5.123%	$156.0866	$156.09	$156.10	$156.10
Purchase #4	$123.93	13.695%	$140.9022	$140.90	$140.90	$140.90
Purchase #5	$103.69	7.717%	$111.6918	$111.69	$111.70	$111.70
Purchase #6	$208.65	3.663%	$216.2928	$216.29	$216.30	$216.30
Purchase #7	$64.58	11.677%	$72.121	$72.12	$72.10	$72.10
7 purchase totals =	$1,016.72		$1,081.8502	$1,081.84	$1,081.85	$1,081.90