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	$109.66	3.146%	$113.1099	$113.11	$113.10	$113.10
Purchase #2	$31.99	11.474%	$35.6605	$35.66	$35.65	$35.70
Purchase #3	$168.98	8.204%	$182.8431	$182.84	$182.85	$182.80
Purchase #4	$123.51	4.345%	$128.8765	$128.88	$128.90	$128.90
Purchase #5	$98.46	7.180%	$105.5294	$105.53	$105.55	$105.50
Purchase #6	$34.74	3.385%	$35.9159	$35.92	$35.90	$35.90
Purchase #7	$164.33	4.807%	$172.2293	$172.23	$172.25	$172.20
7 purchase totals =	$731.67		$774.1646	$774.17	$774.20	$774.10