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	$215.78	6.793%	$230.4379	$230.44	$230.45	$230.40
Purchase #2	$18.80	6.516%	$20.025	$20.03	$20.05	$20.00
Purchase #3	$48.74	11.134%	$54.1667	$54.17	$54.15	$54.20
Purchase #4	$175.46	7.442%	$188.5177	$188.52	$188.50	$188.50
Purchase #5	$141.46	4.641%	$148.0252	$148.03	$148.05	$148.00
Purchase #6	$150.42	11.573%	$167.8281	$167.83	$167.85	$167.80
Purchase #7	$170.86	9.843%	$187.6777	$187.68	$187.70	$187.70
7 purchase totals =	$921.52		$996.6783	$996.70	$996.75	$996.60