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	$148.40	8.817%	$161.4844	$161.48	$161.50	$161.50
Purchase #2	$45.48	11.164%	$50.5574	$50.56	$50.55	$50.60
Purchase #3	$42.25	3.119%	$43.5678	$43.57	$43.55	$43.60
Purchase #4	$230.98	6.181%	$245.2569	$245.26	$245.25	$245.30
Purchase #5	$230.96	8.410%	$250.3837	$250.38	$250.40	$250.40
Purchase #6	$133.31	9.406%	$145.8491	$145.85	$145.85	$145.80
Purchase #7	$200.74	6.733%	$214.2558	$214.26	$214.25	$214.30
7 purchase totals =	$1,032.12		$1,111.3551	$1,111.36	$1,111.35	$1,111.50