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	$65.73	10.208%	$72.4397	$72.44	$72.45	$72.40
Purchase #2	$225.35	12.650%	$253.8568	$253.86	$253.85	$253.90
Purchase #3	$208.77	8.772%	$227.0833	$227.08	$227.10	$227.10
Purchase #4	$75.95	13.385%	$86.1159	$86.12	$86.10	$86.10
Purchase #5	$85.35	7.104%	$91.4133	$91.41	$91.40	$91.40
Purchase #6	$183.79	9.398%	$201.0626	$201.06	$201.05	$201.10
Purchase #7	$173.71	3.573%	$179.9167	$179.92	$179.90	$179.90
7 purchase totals =	$1,018.65		$1,111.8883	$1,111.89	$1,111.85	$1,111.90