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	$35.31	4.323%	$36.8365	$36.84	$36.85	$36.80
Purchase #2	$18.69	13.721%	$21.2545	$21.25	$21.25	$21.30
Purchase #3	$167.95	4.686%	$175.8201	$175.82	$175.80	$175.80
Purchase #4	$28.74	8.185%	$31.0924	$31.09	$31.10	$31.10
Purchase #5	$233.68	12.472%	$262.8246	$262.82	$262.80	$262.80
Purchase #6	$57.93	3.168%	$59.7652	$59.77	$59.75	$59.80
Purchase #7	$100.41	8.608%	$109.0533	$109.05	$109.05	$109.10
7 purchase totals =	$642.71		$696.6466	$696.64	$696.60	$696.70