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	$91.61	11.742%	$102.3668	$102.37	$102.35	$102.40
Purchase #2	$194.32	3.192%	$200.5227	$200.52	$200.50	$200.50
Purchase #3	$33.94	11.711%	$37.9147	$37.91	$37.90	$37.90
Purchase #4	$46.59	10.728%	$51.5882	$51.59	$51.60	$51.60
Purchase #5	$144.50	4.613%	$151.1658	$151.17	$151.15	$151.20
Purchase #6	$41.99	3.107%	$43.2946	$43.29	$43.30	$43.30
Purchase #7	$102.86	3.529%	$106.4899	$106.49	$106.50	$106.50
7 purchase totals =	$655.81		$693.3427	$693.34	$693.30	$693.40