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	$236.88	4.446%	$247.4117	$247.41	$247.40	$247.40
Purchase #2	$147.37	6.481%	$156.921	$156.92	$156.90	$156.90
Purchase #3	$155.92	6.526%	$166.0953	$166.10	$166.10	$166.10
Purchase #4	$109.47	13.429%	$124.1707	$124.17	$124.15	$124.20
Purchase #5	$17.82	3.185%	$18.3876	$18.39	$18.40	$18.40
Purchase #6	$72.92	13.797%	$82.9808	$82.98	$83.00	$83.00
Purchase #7	$244.41	8.591%	$265.4073	$265.41	$265.40	$265.40
7 purchase totals =	$984.79		$1,061.3744	$1,061.38	$1,061.35	$1,061.40