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	$46.90	3.855%	$48.708	$48.71	$48.70	$48.70
Purchase #2	$143.50	5.157%	$150.9003	$150.90	$150.90	$150.90
Purchase #3	$185.86	5.632%	$196.3276	$196.33	$196.35	$196.30
Purchase #4	$191.85	6.238%	$203.8176	$203.82	$203.80	$203.80
Purchase #5	$243.54	9.269%	$266.1137	$266.11	$266.10	$266.10
Purchase #6	$41.42	12.439%	$46.5722	$46.57	$46.55	$46.60
Purchase #7	$249.34	7.685%	$268.5018	$268.50	$268.50	$268.50
7 purchase totals =	$1,102.41		$1,180.9412	$1,180.94	$1,180.90	$1,180.90