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	$173.71	9.671%	$190.5095	$190.51	$190.50	$190.50
Purchase #2	$150.77	10.310%	$166.3144	$166.31	$166.30	$166.30
Purchase #3	$181.33	5.674%	$191.6187	$191.62	$191.60	$191.60
Purchase #4	$202.27	4.568%	$211.5097	$211.51	$211.50	$211.50
Purchase #5	$223.65	3.633%	$231.7752	$231.78	$231.80	$231.80
Purchase #6	$68.80	9.734%	$75.497	$75.50	$75.50	$75.50
Purchase #7	$6.38	11.799%	$7.1328	$7.13	$7.15	$7.10
7 purchase totals =	$1,006.91		$1,074.3573	$1,074.36	$1,074.35	$1,074.30