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	$245.93	11.640%	$274.5563	$274.56	$274.55	$274.60
Purchase #2	$173.69	4.389%	$181.3133	$181.31	$181.30	$181.30
Purchase #3	$49.31	6.460%	$52.4954	$52.50	$52.50	$52.50
Purchase #4	$242.26	5.158%	$254.7558	$254.76	$254.75	$254.80
Purchase #5	$60.86	3.293%	$62.8641	$62.86	$62.85	$62.90
Purchase #6	$10.33	6.787%	$11.0311	$11.03	$11.05	$11.00
Purchase #7	$193.92	11.649%	$216.5097	$216.51	$216.50	$216.50
7 purchase totals =	$976.30		$1,053.5257	$1,053.53	$1,053.50	$1,053.60