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	$121.31	4.699%	$127.0104	$127.01	$127.00	$127.00
Purchase #2	$142.59	7.309%	$153.0119	$153.01	$153.00	$153.00
Purchase #3	$245.78	11.761%	$274.6862	$274.69	$274.70	$274.70
Purchase #4	$24.94	12.641%	$28.0927	$28.09	$28.10	$28.10
Purchase #5	$129.49	13.435%	$146.887	$146.89	$146.90	$146.90
Purchase #6	$96.35	13.609%	$109.4623	$109.46	$109.45	$109.50
Purchase #7	$5.68	8.115%	$6.1409	$6.14	$6.15	$6.10
7 purchase totals =	$766.14		$845.2914	$845.29	$845.30	$845.30