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	$7.38	6.595%	$7.8667	$7.87	$7.85	$7.90
Purchase #2	$7.51	9.433%	$8.2184	$8.22	$8.20	$8.20
Purchase #3	$184.84	6.287%	$196.4609	$196.46	$196.45	$196.50
Purchase #4	$223.42	3.769%	$231.8407	$231.84	$231.85	$231.80
Purchase #5	$199.85	6.151%	$212.1428	$212.14	$212.15	$212.10
Purchase #6	$183.58	3.659%	$190.2972	$190.30	$190.30	$190.30
Purchase #7	$155.54	4.398%	$162.3806	$162.38	$162.40	$162.40
7 purchase totals =	$962.12		$1,009.2073	$1,009.21	$1,009.20	$1,009.20