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	$67.89	12.603%	$76.4462	$76.45	$76.45	$76.40
Purchase #2	$155.88	5.346%	$164.2133	$164.21	$164.20	$164.20
Purchase #3	$86.30	3.591%	$89.399	$89.40	$89.40	$89.40
Purchase #4	$219.50	13.406%	$248.9262	$248.93	$248.95	$248.90
Purchase #5	$94.86	8.794%	$103.202	$103.20	$103.20	$103.20
Purchase #6	$101.72	8.682%	$110.5513	$110.55	$110.55	$110.60
Purchase #7	$208.32	9.564%	$228.2437	$228.24	$228.25	$228.20
7 purchase totals =	$934.47		$1,020.9817	$1,020.98	$1,021.00	$1,020.90