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	$184.50	13.615%	$209.6197	$209.62	$209.60	$209.60
Purchase #2	$158.42	7.548%	$170.3775	$170.38	$170.40	$170.40
Purchase #3	$215.89	11.804%	$241.3737	$241.37	$241.35	$241.40
Purchase #4	$203.86	4.370%	$212.7687	$212.77	$212.75	$212.80
Purchase #5	$222.78	7.227%	$238.8803	$238.88	$238.90	$238.90
Purchase #6	$55.45	7.863%	$59.81	$59.81	$59.80	$59.80
Purchase #7	$215.80	10.298%	$238.0231	$238.02	$238.00	$238.00
7 purchase totals =	$1,256.70		$1,370.8530	$1,370.85	$1,370.80	$1,370.90