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	$67.83	7.866%	$73.1655	$73.17	$73.15	$73.20
Purchase #2	$219.28	5.263%	$230.8207	$230.82	$230.80	$230.80
Purchase #3	$102.72	11.204%	$114.2287	$114.23	$114.25	$114.20
Purchase #4	$139.58	6.404%	$148.5187	$148.52	$148.50	$148.50
Purchase #5	$246.47	7.256%	$264.3539	$264.35	$264.35	$264.40
Purchase #6	$72.25	11.269%	$80.3919	$80.39	$80.40	$80.40
Purchase #7	$85.88	6.215%	$91.2174	$91.22	$91.20	$91.20
7 purchase totals =	$934.01		$1,002.6968	$1,002.70	$1,002.65	$1,002.70