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	$47.65	5.261%	$50.1569	$50.16	$50.15	$50.20
Purchase #2	$242.46	5.239%	$255.1625	$255.16	$255.15	$255.20
Purchase #3	$211.30	9.744%	$231.8891	$231.89	$231.90	$231.90
Purchase #4	$11.42	8.480%	$12.3884	$12.39	$12.40	$12.40
Purchase #5	$68.36	4.233%	$71.2537	$71.25	$71.25	$71.30
Purchase #6	$185.25	13.552%	$210.3551	$210.36	$210.35	$210.40
Purchase #7	$203.34	5.868%	$215.272	$215.27	$215.25	$215.30
7 purchase totals =	$969.78		$1,046.4777	$1,046.48	$1,046.45	$1,046.70