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	$41.31	5.359%	$43.5238	$43.52	$43.50	$43.50
Purchase #2	$214.61	12.571%	$241.5886	$241.59	$241.60	$241.60
Purchase #3	$103.94	6.690%	$110.8936	$110.89	$110.90	$110.90
Purchase #4	$154.63	5.118%	$162.544	$162.54	$162.55	$162.50
Purchase #5	$118.73	11.443%	$132.3163	$132.32	$132.30	$132.30
Purchase #6	$173.52	6.699%	$185.1441	$185.14	$185.15	$185.10
Purchase #7	$244.44	12.524%	$275.0537	$275.05	$275.05	$275.10
7 purchase totals =	$1,051.18		$1,151.0641	$1,151.05	$1,151.05	$1,151.00