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	$104.59	11.435%	$116.5499	$116.55	$116.55	$116.50
Purchase #2	$170.92	4.791%	$179.1088	$179.11	$179.10	$179.10
Purchase #3	$204.49	11.468%	$227.9409	$227.94	$227.95	$227.90
Purchase #4	$152.94	6.482%	$162.8536	$162.85	$162.85	$162.90
Purchase #5	$22.83	12.625%	$25.7123	$25.71	$25.70	$25.70
Purchase #6	$223.90	3.519%	$231.779	$231.78	$231.80	$231.80
Purchase #7	$112.33	13.273%	$127.2396	$127.24	$127.25	$127.20
7 purchase totals =	$992.00		$1,071.1841	$1,071.18	$1,071.20	$1,071.10