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	$109.79	11.243%	$122.1337	$122.13	$122.15	$122.10
Purchase #2	$167.85	10.435%	$185.3651	$185.37	$185.35	$185.40
Purchase #3	$130.49	4.717%	$136.6452	$136.65	$136.65	$136.60
Purchase #4	$164.85	11.639%	$184.0369	$184.04	$184.05	$184.00
Purchase #5	$212.91	7.300%	$228.4524	$228.45	$228.45	$228.50
Purchase #6	$133.46	7.496%	$143.4642	$143.46	$143.45	$143.50
Purchase #7	$140.52	11.238%	$156.3116	$156.31	$156.30	$156.30
7 purchase totals =	$1,059.87		$1,156.4091	$1,156.41	$1,156.40	$1,156.40