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	$103.44	5.532%	$109.1623	$109.16	$109.15	$109.20
Purchase #2	$33.68	7.607%	$36.242	$36.24	$36.25	$36.20
Purchase #3	$241.84	11.439%	$269.5041	$269.50	$269.50	$269.50
Purchase #4	$64.82	8.145%	$70.0996	$70.10	$70.10	$70.10
Purchase #5	$99.96	11.706%	$111.6613	$111.66	$111.65	$111.70
Purchase #6	$205.38	6.229%	$218.1731	$218.17	$218.15	$218.20
Purchase #7	$74.57	11.304%	$82.9994	$83.00	$83.00	$83.00
7 purchase totals =	$823.69		$897.8418	$897.83	$897.80	$897.90