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	$232.61	13.741%	$264.5729	$264.57	$264.55	$264.60
Purchase #2	$211.81	5.223%	$222.8728	$222.87	$222.85	$222.90
Purchase #3	$102.43	8.529%	$111.1663	$111.17	$111.15	$111.20
Purchase #4	$196.79	8.200%	$212.9268	$212.93	$212.95	$212.90
Purchase #5	$41.48	9.106%	$45.2572	$45.26	$45.25	$45.30
Purchase #6	$46.81	9.535%	$51.2733	$51.27	$51.25	$51.30
Purchase #7	$234.33	10.111%	$258.0231	$258.02	$258.00	$258.00
7 purchase totals =	$1,066.26		$1,166.0924	$1,166.09	$1,166.00	$1,166.20