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	$20.74	11.329%	$23.0896	$23.09	$23.10	$23.10
Purchase #2	$185.90	6.468%	$197.924	$197.92	$197.90	$197.90
Purchase #3	$158.51	5.326%	$166.9522	$166.95	$166.95	$167.00
Purchase #4	$55.30	11.132%	$61.456	$61.46	$61.45	$61.50
Purchase #5	$212.77	12.112%	$238.5407	$238.54	$238.55	$238.50
Purchase #6	$242.30	5.692%	$256.0917	$256.09	$256.10	$256.10
Purchase #7	$76.28	3.465%	$78.9231	$78.92	$78.90	$78.90
7 purchase totals =	$951.80		$1,022.9773	$1,022.97	$1,022.95	$1,023.00