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	$51.89	4.306%	$54.1244	$54.12	$54.10	$54.10
Purchase #2	$92.72	4.547%	$96.936	$96.94	$96.95	$96.90
Purchase #3	$98.71	9.758%	$108.3421	$108.34	$108.35	$108.30
Purchase #4	$68.52	5.715%	$72.4359	$72.44	$72.45	$72.40
Purchase #5	$191.61	13.463%	$217.4065	$217.41	$217.40	$217.40
Purchase #6	$172.52	3.624%	$178.7721	$178.77	$178.75	$178.80
Purchase #7	$19.57	4.121%	$20.3765	$20.38	$20.40	$20.40
7 purchase totals =	$695.54		$748.3935	$748.40	$748.40	$748.30