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	$175.76	9.222%	$191.9686	$191.97	$191.95	$192.00
Purchase #2	$153.79	8.518%	$166.8898	$166.89	$166.90	$166.90
Purchase #3	$131.73	10.519%	$145.5867	$145.59	$145.60	$145.60
Purchase #4	$81.44	11.572%	$90.8642	$90.86	$90.85	$90.90
Purchase #5	$230.88	8.144%	$249.6829	$249.68	$249.70	$249.70
Purchase #6	$210.54	10.573%	$232.8004	$232.80	$232.80	$232.80
Purchase #7	$25.53	8.823%	$27.7825	$27.78	$27.80	$27.80
7 purchase totals =	$1,009.67		$1,105.5751	$1,105.57	$1,105.60	$1,105.70