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	$96.34	11.448%	$107.369	$107.37	$107.35	$107.40
Purchase #2	$84.82	6.842%	$90.6234	$90.62	$90.60	$90.60
Purchase #3	$41.68	9.190%	$45.5104	$45.51	$45.50	$45.50
Purchase #4	$71.81	7.692%	$77.3336	$77.33	$77.35	$77.30
Purchase #5	$104.75	6.687%	$111.7546	$111.75	$111.75	$111.80
Purchase #6	$150.46	11.742%	$168.127	$168.13	$168.15	$168.10
Purchase #7	$120.61	8.491%	$130.851	$130.85	$130.85	$130.90
7 purchase totals =	$670.47		$731.5690	$731.56	$731.55	$731.60