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	$202.40	10.446%	$223.5427	$223.54	$223.55	$223.50
Purchase #2	$190.41	3.354%	$196.7964	$196.80	$196.80	$196.80
Purchase #3	$127.56	7.161%	$136.6946	$136.69	$136.70	$136.70
Purchase #4	$100.97	10.542%	$111.6143	$111.61	$111.60	$111.60
Purchase #5	$156.99	7.749%	$169.1552	$169.16	$169.15	$169.20
Purchase #6	$31.79	3.229%	$32.8165	$32.82	$32.80	$32.80
Purchase #7	$245.82	8.836%	$267.5407	$267.54	$267.55	$267.50
7 purchase totals =	$1,055.94		$1,138.1604	$1,138.16	$1,138.15	$1,138.10