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	$246.40	7.756%	$265.5108	$265.51	$265.50	$265.50
Purchase #2	$14.85	5.628%	$15.6858	$15.69	$15.70	$15.70
Purchase #3	$205.48	6.530%	$218.8978	$218.90	$218.90	$218.90
Purchase #4	$65.50	8.591%	$71.1271	$71.13	$71.15	$71.10
Purchase #5	$145.75	4.569%	$152.4093	$152.41	$152.40	$152.40
Purchase #6	$52.30	3.118%	$53.9307	$53.93	$53.95	$53.90
Purchase #7	$110.31	4.598%	$115.3821	$115.38	$115.40	$115.40
7 purchase totals =	$840.59		$892.9436	$892.95	$893.00	$892.90