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	$107.93	4.560%	$112.8516	$112.85	$112.85	$112.90
Purchase #2	$242.64	11.118%	$269.6167	$269.62	$269.60	$269.60
Purchase #3	$203.40	4.172%	$211.8858	$211.89	$211.90	$211.90
Purchase #4	$197.80	7.746%	$213.1216	$213.12	$213.10	$213.10
Purchase #5	$244.32	7.536%	$262.732	$262.73	$262.75	$262.70
Purchase #6	$115.45	10.407%	$127.4649	$127.46	$127.45	$127.50
Purchase #7	$52.59	5.813%	$55.6471	$55.65	$55.65	$55.60
7 purchase totals =	$1,164.13		$1,253.3197	$1,253.32	$1,253.30	$1,253.30