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	$84.74	5.502%	$89.4024	$89.40	$89.40	$89.40
Purchase #2	$182.65	3.576%	$189.1816	$189.18	$189.20	$189.20
Purchase #3	$69.47	12.550%	$78.1885	$78.19	$78.20	$78.20
Purchase #4	$70.60	7.813%	$76.116	$76.12	$76.10	$76.10
Purchase #5	$91.90	13.516%	$104.3212	$104.32	$104.30	$104.30
Purchase #6	$61.90	5.832%	$65.51	$65.51	$65.50	$65.50
Purchase #7	$128.91	10.331%	$142.2277	$142.23	$142.25	$142.20
7 purchase totals =	$690.17		$744.9474	$744.95	$744.95	$744.90