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	$246.25	7.145%	$263.8446	$263.84	$263.85	$263.80
Purchase #2	$54.59	12.166%	$61.2314	$61.23	$61.25	$61.20
Purchase #3	$152.42	5.358%	$160.5867	$160.59	$160.60	$160.60
Purchase #4	$67.47	12.118%	$75.646	$75.65	$75.65	$75.60
Purchase #5	$114.72	7.704%	$123.558	$123.56	$123.55	$123.60
Purchase #6	$79.73	9.724%	$87.4829	$87.48	$87.50	$87.50
Purchase #7	$130.37	9.321%	$142.5218	$142.52	$142.50	$142.50
7 purchase totals =	$845.55		$914.8714	$914.87	$914.90	$914.80