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	$108.53	4.644%	$113.5701	$113.57	$113.55	$113.60
Purchase #2	$186.96	13.346%	$211.9117	$211.91	$211.90	$211.90
Purchase #3	$167.57	4.430%	$174.9934	$174.99	$175.00	$175.00
Purchase #4	$42.62	6.493%	$45.3873	$45.39	$45.40	$45.40
Purchase #5	$67.97	6.581%	$72.4431	$72.44	$72.45	$72.40
Purchase #6	$181.32	8.373%	$196.5019	$196.50	$196.50	$196.50
Purchase #7	$65.94	6.333%	$70.116	$70.12	$70.10	$70.10
7 purchase totals =	$820.91		$884.9235	$884.92	$884.90	$884.90