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	$216.70	6.388%	$230.5428	$230.54	$230.55	$230.50
Purchase #2	$81.72	4.484%	$85.3843	$85.38	$85.40	$85.40
Purchase #3	$180.88	3.733%	$187.6323	$187.63	$187.65	$187.60
Purchase #4	$130.32	11.184%	$144.895	$144.90	$144.90	$144.90
Purchase #5	$116.47	8.765%	$126.6786	$126.68	$126.70	$126.70
Purchase #6	$61.36	6.164%	$65.1422	$65.14	$65.15	$65.10
Purchase #7	$98.84	3.308%	$102.1096	$102.11	$102.10	$102.10
7 purchase totals =	$886.29		$942.3848	$942.38	$942.45	$942.30