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	$89.27	8.254%	$96.6383	$96.64	$96.65	$96.60
Purchase #2	$75.60	13.305%	$85.6586	$85.66	$85.65	$85.70
Purchase #3	$180.67	12.626%	$203.4814	$203.48	$203.50	$203.50
Purchase #4	$235.51	13.554%	$267.431	$267.43	$267.45	$267.40
Purchase #5	$109.41	12.515%	$123.1027	$123.10	$123.10	$123.10
Purchase #6	$113.85	11.757%	$127.2353	$127.24	$127.25	$127.20
Purchase #7	$162.51	11.407%	$181.0475	$181.05	$181.05	$181.00
7 purchase totals =	$966.82		$1,084.5948	$1,084.60	$1,084.65	$1,084.50