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	$91.50	7.647%	$98.497	$98.50	$98.50	$98.50
Purchase #2	$58.93	4.667%	$61.6803	$61.68	$61.70	$61.70
Purchase #3	$144.84	11.104%	$160.923	$160.92	$160.90	$160.90
Purchase #4	$50.92	7.740%	$54.8612	$54.86	$54.85	$54.90
Purchase #5	$106.75	12.254%	$119.8311	$119.83	$119.85	$119.80
Purchase #6	$58.99	11.870%	$65.9921	$65.99	$66.00	$66.00
Purchase #7	$42.65	7.364%	$45.7907	$45.79	$45.80	$45.80
7 purchase totals =	$554.58		$607.5754	$607.57	$607.60	$607.60