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	$94.73	8.774%	$103.0416	$103.04	$103.05	$103.00
Purchase #2	$170.96	9.307%	$186.8712	$186.87	$186.85	$186.90
Purchase #3	$151.31	10.150%	$166.668	$166.67	$166.65	$166.70
Purchase #4	$57.34	11.632%	$64.0098	$64.01	$64.00	$64.00
Purchase #5	$250.35	10.659%	$277.0348	$277.03	$277.05	$277.00
Purchase #6	$24.37	11.131%	$27.0826	$27.08	$27.10	$27.10
Purchase #7	$168.72	11.566%	$188.2342	$188.23	$188.25	$188.20
7 purchase totals =	$917.78		$1,012.9422	$1,012.93	$1,012.95	$1,012.90