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	$232.85	7.735%	$250.8609	$250.86	$250.85	$250.90
Purchase #2	$227.47	12.507%	$255.9197	$255.92	$255.90	$255.90
Purchase #3	$56.73	5.114%	$59.6312	$59.63	$59.65	$59.60
Purchase #4	$209.69	13.525%	$238.0506	$238.05	$238.05	$238.10
Purchase #5	$75.72	9.242%	$82.718	$82.72	$82.70	$82.70
Purchase #6	$95.26	7.440%	$102.3473	$102.35	$102.35	$102.30
Purchase #7	$189.67	7.413%	$203.7302	$203.73	$203.75	$203.70
7 purchase totals =	$1,087.39		$1,193.2579	$1,193.26	$1,193.25	$1,193.20