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	$83.78	8.128%	$90.5896	$90.59	$90.60	$90.60
Purchase #2	$200.74	7.771%	$216.3395	$216.34	$216.35	$216.30
Purchase #3	$104.95	9.155%	$114.5582	$114.56	$114.55	$114.60
Purchase #4	$84.97	5.150%	$89.346	$89.35	$89.35	$89.30
Purchase #5	$155.92	11.765%	$174.264	$174.26	$174.25	$174.30
Purchase #6	$64.27	4.185%	$66.9597	$66.96	$66.95	$67.00
Purchase #7	$41.26	3.290%	$42.6175	$42.62	$42.60	$42.60
7 purchase totals =	$735.89		$794.6745	$794.68	$794.65	$794.70