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	$175.57	5.348%	$184.9595	$184.96	$184.95	$185.00
Purchase #2	$62.45	5.160%	$65.6724	$65.67	$65.65	$65.70
Purchase #3	$114.61	6.570%	$122.1399	$122.14	$122.15	$122.10
Purchase #4	$81.25	6.267%	$86.3419	$86.34	$86.35	$86.30
Purchase #5	$10.39	9.505%	$11.3776	$11.38	$11.40	$11.40
Purchase #6	$174.27	12.649%	$196.3134	$196.31	$196.30	$196.30
Purchase #7	$72.34	11.246%	$80.4754	$80.48	$80.50	$80.50
7 purchase totals =	$690.88		$747.2801	$747.28	$747.30	$747.30