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	$221.59	5.278%	$233.2855	$233.29	$233.30	$233.30
Purchase #2	$136.59	4.318%	$142.488	$142.49	$142.50	$142.50
Purchase #3	$197.36	5.142%	$207.5083	$207.51	$207.50	$207.50
Purchase #4	$179.86	6.283%	$191.1606	$191.16	$191.15	$191.20
Purchase #5	$151.73	4.673%	$158.8203	$158.82	$158.80	$158.80
Purchase #6	$98.90	10.295%	$109.0818	$109.08	$109.10	$109.10
Purchase #7	$172.71	3.782%	$179.2419	$179.24	$179.25	$179.20
7 purchase totals =	$1,158.74		$1,221.5864	$1,221.59	$1,221.60	$1,221.60