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	$167.90	10.405%	$185.37	$185.37	$185.35	$185.40
Purchase #2	$141.37	10.741%	$156.5546	$156.55	$156.55	$156.60
Purchase #3	$54.35	4.265%	$56.668	$56.67	$56.65	$56.70
Purchase #4	$199.98	5.630%	$211.2389	$211.24	$211.25	$211.20
Purchase #5	$92.32	12.236%	$103.6163	$103.62	$103.60	$103.60
Purchase #6	$88.95	8.823%	$96.7981	$96.80	$96.80	$96.80
Purchase #7	$176.67	5.211%	$185.8763	$185.88	$185.90	$185.90
7 purchase totals =	$921.54		$996.1222	$996.13	$996.10	$996.20