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	$172.75	10.827%	$191.4536	$191.45	$191.45	$191.50
Purchase #2	$116.45	7.804%	$125.5378	$125.54	$125.55	$125.50
Purchase #3	$148.66	4.416%	$155.2248	$155.22	$155.20	$155.20
Purchase #4	$77.64	10.538%	$85.8217	$85.82	$85.80	$85.80
Purchase #5	$90.37	13.215%	$102.3124	$102.31	$102.30	$102.30
Purchase #6	$70.82	10.344%	$78.1456	$78.15	$78.15	$78.10
Purchase #7	$89.93	7.598%	$96.7629	$96.76	$96.75	$96.80
7 purchase totals =	$766.62		$835.2588	$835.25	$835.20	$835.20