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	$151.49	10.285%	$167.0707	$167.07	$167.05	$167.10
Purchase #2	$225.75	13.207%	$255.5648	$255.56	$255.55	$255.60
Purchase #3	$56.27	8.704%	$61.1677	$61.17	$61.15	$61.20
Purchase #4	$113.49	10.383%	$125.2737	$125.27	$125.25	$125.30
Purchase #5	$31.96	12.104%	$35.8284	$35.83	$35.85	$35.80
Purchase #6	$180.86	5.844%	$191.4295	$191.43	$191.45	$191.40
Purchase #7	$146.61	12.489%	$164.9201	$164.92	$164.90	$164.90
7 purchase totals =	$906.43		$1,001.2549	$1,001.25	$1,001.20	$1,001.30