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	$123.30	3.386%	$127.4749	$127.47	$127.45	$127.50
Purchase #2	$71.46	9.507%	$78.2537	$78.25	$78.25	$78.30
Purchase #3	$76.98	9.731%	$84.4709	$84.47	$84.45	$84.50
Purchase #4	$152.43	8.406%	$165.2433	$165.24	$165.25	$165.20
Purchase #5	$90.88	9.507%	$99.52	$99.52	$99.50	$99.50
Purchase #6	$87.66	9.489%	$95.9781	$95.98	$96.00	$96.00
Purchase #7	$237.55	11.135%	$264.0012	$264.00	$264.00	$264.00
7 purchase totals =	$840.26		$914.9421	$914.93	$914.90	$915.00