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	$157.42	7.859%	$169.7916	$169.79	$169.80	$169.80
Purchase #2	$56.91	8.219%	$61.5874	$61.59	$61.60	$61.60
Purchase #3	$219.60	10.177%	$241.9487	$241.95	$241.95	$241.90
Purchase #4	$97.62	10.218%	$107.5948	$107.59	$107.60	$107.60
Purchase #5	$80.70	10.799%	$89.4148	$89.41	$89.40	$89.40
Purchase #6	$13.28	9.298%	$14.5148	$14.51	$14.50	$14.50
Purchase #7	$97.76	3.586%	$101.2657	$101.27	$101.25	$101.30
7 purchase totals =	$723.29		$786.1178	$786.11	$786.10	$786.10