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	$72.64	10.763%	$80.4582	$80.46	$80.45	$80.50
Purchase #2	$86.40	12.485%	$97.187	$97.19	$97.20	$97.20
Purchase #3	$159.40	9.706%	$174.8714	$174.87	$174.85	$174.90
Purchase #4	$148.52	12.851%	$167.6063	$167.61	$167.60	$167.60
Purchase #5	$64.53	11.832%	$72.1652	$72.17	$72.15	$72.20
Purchase #6	$241.64	9.583%	$264.7964	$264.80	$264.80	$264.80
Purchase #7	$148.97	4.313%	$155.3951	$155.40	$155.40	$155.40
7 purchase totals =	$922.10		$1,012.4796	$1,012.50	$1,012.45	$1,012.60