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	$168.37	6.354%	$179.0682	$179.07	$179.05	$179.10
Purchase #2	$173.37	6.845%	$185.2372	$185.24	$185.25	$185.20
Purchase #3	$35.75	3.592%	$37.0341	$37.03	$37.05	$37.00
Purchase #4	$29.89	11.629%	$33.3659	$33.37	$33.35	$33.40
Purchase #5	$97.46	7.556%	$104.8241	$104.82	$104.80	$104.80
Purchase #6	$244.76	10.690%	$270.9248	$270.92	$270.90	$270.90
Purchase #7	$146.63	4.206%	$152.7973	$152.80	$152.80	$152.80
7 purchase totals =	$896.23		$963.2516	$963.25	$963.20	$963.20