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	$142.91	6.551%	$152.272	$152.27	$152.25	$152.30
Purchase #2	$18.80	13.815%	$21.3972	$21.40	$21.40	$21.40
Purchase #3	$173.26	13.485%	$196.6241	$196.62	$196.60	$196.60
Purchase #4	$30.56	12.113%	$34.2617	$34.26	$34.25	$34.30
Purchase #5	$25.94	4.316%	$27.0596	$27.06	$27.05	$27.10
Purchase #6	$128.33	11.313%	$142.848	$142.85	$142.85	$142.80
Purchase #7	$85.45	13.688%	$97.1464	$97.15	$97.15	$97.10
7 purchase totals =	$605.25		$671.6090	$671.61	$671.55	$671.60