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	$79.43	13.832%	$90.4168	$90.42	$90.40	$90.40
Purchase #2	$24.33	6.699%	$25.9599	$25.96	$25.95	$26.00
Purchase #3	$232.81	9.702%	$255.3972	$255.40	$255.40	$255.40
Purchase #4	$208.77	6.858%	$223.0874	$223.09	$223.10	$223.10
Purchase #5	$169.58	12.722%	$191.154	$191.15	$191.15	$191.20
Purchase #6	$75.56	9.673%	$82.8689	$82.87	$82.85	$82.90
Purchase #7	$241.38	9.399%	$264.0673	$264.07	$264.05	$264.10
7 purchase totals =	$1,031.86		$1,132.9515	$1,132.96	$1,132.90	$1,133.10