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	$139.92	9.208%	$152.8038	$152.80	$152.80	$152.80
Purchase #2	$218.67	5.363%	$230.3973	$230.40	$230.40	$230.40
Purchase #3	$105.90	7.800%	$114.1602	$114.16	$114.15	$114.20
Purchase #4	$114.32	9.702%	$125.4113	$125.41	$125.40	$125.40
Purchase #5	$182.42	7.642%	$196.3605	$196.36	$196.35	$196.40
Purchase #6	$131.57	3.448%	$136.1065	$136.11	$136.10	$136.10
Purchase #7	$48.33	8.857%	$52.6106	$52.61	$52.60	$52.60
7 purchase totals =	$941.13		$1,007.8502	$1,007.85	$1,007.80	$1,007.90