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	$200.77	7.206%	$215.2375	$215.24	$215.25	$215.20
Purchase #2	$106.32	9.393%	$116.3066	$116.31	$116.30	$116.30
Purchase #3	$134.93	13.371%	$152.9715	$152.97	$152.95	$153.00
Purchase #4	$118.49	7.245%	$127.0746	$127.07	$127.05	$127.10
Purchase #5	$167.26	3.234%	$172.6692	$172.67	$172.65	$172.70
Purchase #6	$227.40	10.171%	$250.5289	$250.53	$250.55	$250.50
Purchase #7	$145.67	6.302%	$154.8501	$154.85	$154.85	$154.90
7 purchase totals =	$1,100.84		$1,189.6384	$1,189.64	$1,189.60	$1,189.70