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	$56.70	4.559%	$59.285	$59.29	$59.30	$59.30
Purchase #2	$45.39	7.490%	$48.7897	$48.79	$48.80	$48.80
Purchase #3	$105.46	11.482%	$117.5689	$117.57	$117.55	$117.60
Purchase #4	$66.26	10.616%	$73.2942	$73.29	$73.30	$73.30
Purchase #5	$170.59	6.293%	$181.3252	$181.33	$181.35	$181.30
Purchase #6	$49.68	6.433%	$52.8759	$52.88	$52.90	$52.90
Purchase #7	$151.52	10.280%	$167.0963	$167.10	$167.10	$167.10
7 purchase totals =	$645.60		$700.2352	$700.25	$700.30	$700.30