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	$175.34	12.317%	$196.9366	$196.94	$196.95	$196.90
Purchase #2	$244.82	8.780%	$266.3152	$266.32	$266.30	$266.30
Purchase #3	$216.83	3.216%	$223.8033	$223.80	$223.80	$223.80
Purchase #4	$19.79	5.565%	$20.8913	$20.89	$20.90	$20.90
Purchase #5	$99.31	9.473%	$108.7176	$108.72	$108.70	$108.70
Purchase #6	$160.86	5.301%	$169.3872	$169.39	$169.40	$169.40
Purchase #7	$204.82	4.640%	$214.3236	$214.32	$214.30	$214.30
7 purchase totals =	$1,121.77		$1,200.3748	$1,200.38	$1,200.35	$1,200.30