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	$141.81	6.399%	$150.8844	$150.88	$150.90	$150.90
Purchase #2	$211.50	5.566%	$223.2721	$223.27	$223.25	$223.30
Purchase #3	$41.81	13.824%	$47.5898	$47.59	$47.60	$47.60
Purchase #4	$73.44	7.143%	$78.6858	$78.69	$78.70	$78.70
Purchase #5	$41.73	9.581%	$45.7282	$45.73	$45.75	$45.70
Purchase #6	$117.92	13.757%	$134.1423	$134.14	$134.15	$134.10
Purchase #7	$40.74	11.126%	$45.2727	$45.27	$45.25	$45.30
7 purchase totals =	$668.95		$725.5753	$725.57	$725.60	$725.60