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	$174.97	12.279%	$196.4546	$196.45	$196.45	$196.50
Purchase #2	$27.29	8.811%	$29.6945	$29.69	$29.70	$29.70
Purchase #3	$151.82	10.247%	$167.377	$167.38	$167.40	$167.40
Purchase #4	$97.70	13.619%	$111.0058	$111.01	$111.00	$111.00
Purchase #5	$73.59	11.646%	$82.1603	$82.16	$82.15	$82.20
Purchase #6	$222.56	5.646%	$235.1257	$235.13	$235.15	$235.10
Purchase #7	$75.69	8.515%	$82.135	$82.14	$82.15	$82.10
7 purchase totals =	$823.62		$903.9529	$903.96	$904.00	$904.00