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	$118.93	9.675%	$130.4365	$130.44	$130.45	$130.40
Purchase #2	$139.92	8.341%	$151.5907	$151.59	$151.60	$151.60
Purchase #3	$69.89	12.598%	$78.6947	$78.69	$78.70	$78.70
Purchase #4	$81.77	4.347%	$85.3245	$85.32	$85.30	$85.30
Purchase #5	$61.44	9.138%	$67.0544	$67.05	$67.05	$67.10
Purchase #6	$184.96	11.851%	$206.8796	$206.88	$206.90	$206.90
Purchase #7	$5.84	8.823%	$6.3553	$6.36	$6.35	$6.40
7 purchase totals =	$662.75		$726.3357	$726.33	$726.35	$726.40