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	$111.83	12.398%	$125.6947	$125.69	$125.70	$125.70
Purchase #2	$35.29	6.783%	$37.6837	$37.68	$37.70	$37.70
Purchase #3	$146.29	6.787%	$156.2187	$156.22	$156.20	$156.20
Purchase #4	$125.25	12.872%	$141.3722	$141.37	$141.35	$141.40
Purchase #5	$52.46	3.209%	$54.1434	$54.14	$54.15	$54.10
Purchase #6	$241.97	8.637%	$262.8689	$262.87	$262.85	$262.90
Purchase #7	$116.77	12.444%	$131.3009	$131.30	$131.30	$131.30
7 purchase totals =	$829.86		$909.2825	$909.27	$909.25	$909.30