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	$174.61	9.692%	$191.5332	$191.53	$191.55	$191.50
Purchase #2	$111.99	8.342%	$121.3322	$121.33	$121.35	$121.30
Purchase #3	$199.58	9.373%	$218.2866	$218.29	$218.30	$218.30
Purchase #4	$243.98	4.869%	$255.8594	$255.86	$255.85	$255.90
Purchase #5	$135.98	11.124%	$151.1064	$151.11	$151.10	$151.10
Purchase #6	$102.79	11.658%	$114.7733	$114.77	$114.75	$114.80
Purchase #7	$7.56	11.442%	$8.425	$8.43	$8.45	$8.40
7 purchase totals =	$976.49		$1,061.3161	$1,061.32	$1,061.35	$1,061.30