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	$71.65	10.103%	$78.8888	$78.89	$78.90	$78.90
Purchase #2	$94.64	9.488%	$103.6194	$103.62	$103.60	$103.60
Purchase #3	$88.76	3.852%	$92.179	$92.18	$92.20	$92.20
Purchase #4	$142.25	10.668%	$157.4252	$157.43	$157.45	$157.40
Purchase #5	$232.71	12.435%	$261.6475	$261.65	$261.65	$261.60
Purchase #6	$246.29	12.240%	$276.4359	$276.44	$276.45	$276.40
Purchase #7	$47.86	11.675%	$53.4477	$53.45	$53.45	$53.40
7 purchase totals =	$924.16		$1,023.6435	$1,023.66	$1,023.70	$1,023.50