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	$37.96	9.131%	$41.4261	$41.43	$41.45	$41.40
Purchase #2	$210.98	6.114%	$223.8793	$223.88	$223.90	$223.90
Purchase #3	$48.69	12.791%	$54.9179	$54.92	$54.90	$54.90
Purchase #4	$69.58	12.563%	$78.3213	$78.32	$78.30	$78.30
Purchase #5	$228.53	12.258%	$256.5432	$256.54	$256.55	$256.50
Purchase #6	$139.88	5.186%	$147.1342	$147.13	$147.15	$147.10
Purchase #7	$133.81	6.183%	$142.0835	$142.08	$142.10	$142.10
7 purchase totals =	$869.43		$944.3055	$944.30	$944.35	$944.20