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	$219.49	10.429%	$242.3806	$242.38	$242.40	$242.40
Purchase #2	$217.84	4.146%	$226.8716	$226.87	$226.85	$226.90
Purchase #3	$76.28	13.433%	$86.5267	$86.53	$86.55	$86.50
Purchase #4	$124.33	13.106%	$140.6247	$140.62	$140.60	$140.60
Purchase #5	$84.84	13.326%	$96.1458	$96.15	$96.15	$96.10
Purchase #6	$78.41	5.236%	$82.5155	$82.52	$82.50	$82.50
Purchase #7	$203.97	6.794%	$217.8277	$217.83	$217.85	$217.80
7 purchase totals =	$1,005.16		$1,092.8926	$1,092.90	$1,092.90	$1,092.80