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	$118.87	6.865%	$127.0304	$127.03	$127.05	$127.00
Purchase #2	$58.77	11.524%	$65.5427	$65.54	$65.55	$65.50
Purchase #3	$184.44	12.736%	$207.9303	$207.93	$207.95	$207.90
Purchase #4	$160.88	12.590%	$181.1348	$181.13	$181.15	$181.10
Purchase #5	$32.45	10.382%	$35.819	$35.82	$35.80	$35.80
Purchase #6	$82.50	11.434%	$91.9331	$91.93	$91.95	$91.90
Purchase #7	$187.91	10.702%	$208.0201	$208.02	$208.00	$208.00
7 purchase totals =	$825.82		$917.4104	$917.40	$917.45	$917.20