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	$228.26	8.621%	$247.9383	$247.94	$247.95	$247.90
Purchase #2	$80.90	7.700%	$87.1293	$87.13	$87.15	$87.10
Purchase #3	$59.73	13.460%	$67.7697	$67.77	$67.75	$67.80
Purchase #4	$149.33	12.442%	$167.9096	$167.91	$167.90	$167.90
Purchase #5	$155.83	4.314%	$162.5525	$162.55	$162.55	$162.60
Purchase #6	$90.96	4.617%	$95.1596	$95.16	$95.15	$95.20
Purchase #7	$163.26	5.110%	$171.6026	$171.60	$171.60	$171.60
7 purchase totals =	$928.27		$1,000.0616	$1,000.06	$1,000.05	$1,000.10