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	$242.66	9.345%	$265.3366	$265.34	$265.35	$265.30
Purchase #2	$9.70	6.570%	$10.3373	$10.34	$10.35	$10.30
Purchase #3	$53.74	13.738%	$61.1228	$61.12	$61.10	$61.10
Purchase #4	$51.83	6.108%	$54.9958	$55.00	$55.00	$55.00
Purchase #5	$103.37	10.558%	$114.2838	$114.28	$114.30	$114.30
Purchase #6	$82.89	6.346%	$88.1502	$88.15	$88.15	$88.20
Purchase #7	$111.70	5.216%	$117.5263	$117.53	$117.55	$117.50
7 purchase totals =	$655.89		$711.7528	$711.76	$711.80	$711.70