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	$35.91	3.185%	$37.0537	$37.05	$37.05	$37.10
Purchase #2	$102.28	10.225%	$112.7381	$112.74	$112.75	$112.70
Purchase #3	$85.56	8.180%	$92.5588	$92.56	$92.55	$92.60
Purchase #4	$12.56	7.300%	$13.4769	$13.48	$13.50	$13.50
Purchase #5	$214.67	9.435%	$234.9241	$234.92	$234.90	$234.90
Purchase #6	$66.49	7.526%	$71.494	$71.49	$71.50	$71.50
Purchase #7	$249.91	13.192%	$282.8781	$282.88	$282.90	$282.90
7 purchase totals =	$767.38		$845.1237	$845.12	$845.15	$845.20