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	$71.92	3.543%	$74.4681	$74.47	$74.45	$74.50
Purchase #2	$58.89	11.386%	$65.5952	$65.60	$65.60	$65.60
Purchase #3	$6.67	5.683%	$7.0491	$7.05	$7.05	$7.00
Purchase #4	$216.31	3.218%	$223.2709	$223.27	$223.25	$223.30
Purchase #5	$38.35	7.250%	$41.1304	$41.13	$41.15	$41.10
Purchase #6	$20.44	11.404%	$22.771	$22.77	$22.75	$22.80
Purchase #7	$236.29	9.863%	$259.5953	$259.60	$259.60	$259.60
7 purchase totals =	$648.87		$693.8800	$693.89	$693.85	$693.90