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	$232.89	7.436%	$250.2077	$250.21	$250.20	$250.20
Purchase #2	$39.44	13.791%	$44.8792	$44.88	$44.90	$44.90
Purchase #3	$48.58	7.742%	$52.3411	$52.34	$52.35	$52.30
Purchase #4	$152.40	9.254%	$166.5031	$166.50	$166.50	$166.50
Purchase #5	$139.64	3.377%	$144.3556	$144.36	$144.35	$144.40
Purchase #6	$152.92	6.501%	$162.8613	$162.86	$162.85	$162.90
Purchase #7	$164.37	5.584%	$173.5484	$173.55	$173.55	$173.50
7 purchase totals =	$930.24		$994.6964	$994.70	$994.70	$994.70