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	$94.49	4.757%	$98.9849	$98.98	$99.00	$99.00
Purchase #2	$204.85	4.740%	$214.5599	$214.56	$214.55	$214.60
Purchase #3	$43.52	3.594%	$45.0841	$45.08	$45.10	$45.10
Purchase #4	$139.52	9.112%	$152.2331	$152.23	$152.25	$152.20
Purchase #5	$18.79	8.320%	$20.3533	$20.35	$20.35	$20.40
Purchase #6	$40.38	8.622%	$43.8616	$43.86	$43.85	$43.90
Purchase #7	$244.39	7.500%	$262.7193	$262.72	$262.70	$262.70
7 purchase totals =	$785.94		$837.7962	$837.78	$837.80	$837.90