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	$97.94	13.767%	$111.4234	$111.42	$111.40	$111.40
Purchase #2	$92.63	5.415%	$97.6459	$97.65	$97.65	$97.60
Purchase #3	$216.90	4.316%	$226.2614	$226.26	$226.25	$226.30
Purchase #4	$40.41	6.794%	$43.1555	$43.16	$43.15	$43.20
Purchase #5	$96.54	10.383%	$106.5637	$106.56	$106.55	$106.60
Purchase #6	$185.38	3.530%	$191.9239	$191.92	$191.90	$191.90
Purchase #7	$108.36	7.617%	$116.6138	$116.61	$116.60	$116.60
7 purchase totals =	$838.16		$893.5876	$893.58	$893.50	$893.60