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	$245.96	7.513%	$264.439	$264.44	$264.45	$264.40
Purchase #2	$53.80	10.357%	$59.3721	$59.37	$59.35	$59.40
Purchase #3	$242.66	6.394%	$258.1757	$258.18	$258.20	$258.20
Purchase #4	$80.78	10.461%	$89.2304	$89.23	$89.25	$89.20
Purchase #5	$167.95	13.653%	$190.8802	$190.88	$190.90	$190.90
Purchase #6	$168.97	4.132%	$175.9518	$175.95	$175.95	$176.00
Purchase #7	$155.81	13.782%	$177.2837	$177.28	$177.30	$177.30
7 purchase totals =	$1,115.93		$1,215.3329	$1,215.33	$1,215.40	$1,215.40