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	$164.31	13.812%	$187.0045	$187.00	$187.00	$187.00
Purchase #2	$173.95	7.801%	$187.5198	$187.52	$187.50	$187.50
Purchase #3	$180.39	8.723%	$196.1254	$196.13	$196.15	$196.10
Purchase #4	$213.40	10.444%	$235.6875	$235.69	$235.70	$235.70
Purchase #5	$106.58	5.210%	$112.1328	$112.13	$112.15	$112.10
Purchase #6	$249.59	10.393%	$275.5299	$275.53	$275.55	$275.50
Purchase #7	$202.89	9.827%	$222.828	$222.83	$222.85	$222.80
7 purchase totals =	$1,291.11		$1,416.8279	$1,416.83	$1,416.90	$1,416.70