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	$173.83	7.516%	$186.8951	$186.90	$186.90	$186.90
Purchase #2	$10.85	13.599%	$12.3255	$12.33	$12.35	$12.30
Purchase #3	$244.91	4.767%	$256.5849	$256.58	$256.60	$256.60
Purchase #4	$81.50	8.577%	$88.4903	$88.49	$88.50	$88.50
Purchase #5	$167.97	13.560%	$190.7467	$190.75	$190.75	$190.70
Purchase #6	$120.60	6.865%	$128.8792	$128.88	$128.90	$128.90
Purchase #7	$205.87	8.213%	$222.7781	$222.78	$222.80	$222.80
7 purchase totals =	$1,005.53		$1,086.6998	$1,086.71	$1,086.80	$1,086.70