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	$117.33	12.682%	$132.2098	$132.21	$132.20	$132.20
Purchase #2	$237.29	3.274%	$245.0589	$245.06	$245.05	$245.10
Purchase #3	$22.93	11.360%	$25.5348	$25.53	$25.55	$25.50
Purchase #4	$240.38	12.452%	$270.3121	$270.31	$270.30	$270.30
Purchase #5	$43.26	5.499%	$45.6389	$45.64	$45.65	$45.60
Purchase #6	$77.46	7.172%	$83.0154	$83.02	$83.00	$83.00
Purchase #7	$166.72	11.320%	$185.5927	$185.59	$185.60	$185.60
7 purchase totals =	$905.37		$987.3626	$987.36	$987.35	$987.30