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	$162.44	11.365%	$180.9013	$180.90	$180.90	$180.90
Purchase #2	$169.36	8.411%	$183.6049	$183.60	$183.60	$183.60
Purchase #3	$64.77	8.791%	$70.4639	$70.46	$70.45	$70.50
Purchase #4	$7.44	6.853%	$7.9499	$7.95	$7.95	$7.90
Purchase #5	$111.74	11.129%	$124.1755	$124.18	$124.20	$124.20
Purchase #6	$57.98	9.350%	$63.4011	$63.40	$63.40	$63.40
Purchase #7	$33.63	10.674%	$37.2197	$37.22	$37.20	$37.20
7 purchase totals =	$607.36		$667.7163	$667.71	$667.70	$667.70