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	$163.36	6.435%	$173.8722	$173.87	$173.85	$173.90
Purchase #2	$58.74	6.726%	$62.6909	$62.69	$62.70	$62.70
Purchase #3	$196.96	13.162%	$222.8839	$222.88	$222.90	$222.90
Purchase #4	$196.77	7.306%	$211.146	$211.15	$211.15	$211.10
Purchase #5	$213.42	6.134%	$226.5112	$226.51	$226.50	$226.50
Purchase #6	$87.26	3.869%	$90.6361	$90.64	$90.65	$90.60
Purchase #7	$250.42	9.312%	$273.7391	$273.74	$273.75	$273.70
7 purchase totals =	$1,166.93		$1,261.4794	$1,261.48	$1,261.50	$1,261.40