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	$229.45	6.142%	$243.5428	$243.54	$243.55	$243.50
Purchase #2	$165.77	4.667%	$173.5065	$173.51	$173.50	$173.50
Purchase #3	$238.83	11.620%	$266.582	$266.58	$266.60	$266.60
Purchase #4	$83.88	13.788%	$95.4454	$95.45	$95.45	$95.40
Purchase #5	$68.41	3.665%	$70.9172	$70.92	$70.90	$70.90
Purchase #6	$96.41	13.225%	$109.1602	$109.16	$109.15	$109.20
Purchase #7	$176.85	7.479%	$190.0766	$190.08	$190.10	$190.10
7 purchase totals =	$1,059.60		$1,149.2307	$1,149.24	$1,149.25	$1,149.20