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	$71.32	9.448%	$78.0583	$78.06	$78.05	$78.10
Purchase #2	$146.97	12.761%	$165.7248	$165.72	$165.70	$165.70
Purchase #3	$140.72	13.290%	$159.4217	$159.42	$159.40	$159.40
Purchase #4	$248.57	3.832%	$258.0952	$258.10	$258.10	$258.10
Purchase #5	$134.92	7.811%	$145.4586	$145.46	$145.45	$145.50
Purchase #6	$108.34	5.596%	$114.4027	$114.40	$114.40	$114.40
Purchase #7	$203.88	5.567%	$215.23	$215.23	$215.25	$215.20
7 purchase totals =	$1,054.72		$1,136.3913	$1,136.39	$1,136.35	$1,136.40