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	$33.30	7.438%	$35.7769	$35.78	$35.80	$35.80
Purchase #2	$42.33	8.303%	$45.8447	$45.84	$45.85	$45.80
Purchase #3	$33.86	12.301%	$38.0251	$38.03	$38.05	$38.00
Purchase #4	$14.53	8.349%	$15.7431	$15.74	$15.75	$15.70
Purchase #5	$19.83	5.279%	$20.8768	$20.88	$20.90	$20.90
Purchase #6	$85.26	4.801%	$89.3533	$89.35	$89.35	$89.40
Purchase #7	$42.64	8.817%	$46.3996	$46.40	$46.40	$46.40
7 purchase totals =	$271.75		$292.0195	$292.02	$292.10	$292.00