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	$40.29	12.381%	$45.2783	$45.28	$45.30	$45.30
Purchase #2	$178.83	5.357%	$188.4099	$188.41	$188.40	$188.40
Purchase #3	$94.65	11.593%	$105.6228	$105.62	$105.60	$105.60
Purchase #4	$141.40	7.845%	$152.4928	$152.49	$152.50	$152.50
Purchase #5	$129.31	13.585%	$146.8768	$146.88	$146.90	$146.90
Purchase #6	$164.82	10.472%	$182.08	$182.08	$182.10	$182.10
Purchase #7	$191.84	3.628%	$198.8	$198.80	$198.80	$198.80
7 purchase totals =	$941.14		$1,019.5606	$1,019.56	$1,019.60	$1,019.60