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	$63.77	13.449%	$72.3464	$72.35	$72.35	$72.30
Purchase #2	$83.98	10.453%	$92.7584	$92.76	$92.75	$92.80
Purchase #3	$185.82	5.717%	$196.4433	$196.44	$196.45	$196.40
Purchase #4	$192.34	11.115%	$213.7186	$213.72	$213.70	$213.70
Purchase #5	$182.27	12.798%	$205.5969	$205.60	$205.60	$205.60
Purchase #6	$102.71	11.264%	$114.2793	$114.28	$114.30	$114.30
Purchase #7	$201.35	10.339%	$222.1676	$222.17	$222.15	$222.20
7 purchase totals =	$1,012.24		$1,117.3105	$1,117.32	$1,117.30	$1,117.30