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	$184.37	4.209%	$192.1301	$192.13	$192.15	$192.10
Purchase #2	$139.67	9.220%	$152.5476	$152.55	$152.55	$152.50
Purchase #3	$38.32	9.494%	$41.9581	$41.96	$41.95	$42.00
Purchase #4	$68.32	5.413%	$72.0182	$72.02	$72.00	$72.00
Purchase #5	$170.87	6.521%	$182.0124	$182.01	$182.00	$182.00
Purchase #6	$87.74	11.117%	$97.4941	$97.49	$97.50	$97.50
Purchase #7	$248.47	7.152%	$266.2406	$266.24	$266.25	$266.20
7 purchase totals =	$937.76		$1,004.4011	$1,004.40	$1,004.40	$1,004.30