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	$23.98	4.602%	$25.0836	$25.08	$25.10	$25.10
Purchase #2	$72.87	7.231%	$78.1392	$78.14	$78.15	$78.10
Purchase #3	$242.36	3.392%	$250.5809	$250.58	$250.60	$250.60
Purchase #4	$100.33	3.463%	$103.8044	$103.80	$103.80	$103.80
Purchase #5	$88.47	12.502%	$99.5305	$99.53	$99.55	$99.50
Purchase #6	$96.40	8.863%	$104.9439	$104.94	$104.95	$104.90
Purchase #7	$223.56	4.274%	$233.115	$233.12	$233.10	$233.10
7 purchase totals =	$847.97		$895.1975	$895.19	$895.25	$895.10