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	$127.46	4.592%	$133.313	$133.31	$133.30	$133.30
Purchase #2	$41.28	11.837%	$46.1663	$46.17	$46.15	$46.20
Purchase #3	$202.50	9.670%	$222.0818	$222.08	$222.10	$222.10
Purchase #4	$184.86	6.396%	$196.6836	$196.68	$196.70	$196.70
Purchase #5	$20.67	3.477%	$21.3887	$21.39	$21.40	$21.40
Purchase #6	$17.29	9.313%	$18.9002	$18.90	$18.90	$18.90
Purchase #7	$42.35	8.200%	$45.8227	$45.82	$45.80	$45.80
7 purchase totals =	$636.41		$684.3563	$684.35	$684.35	$684.40