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	$200.86	13.657%	$228.2915	$228.29	$228.30	$228.30
Purchase #2	$54.51	9.301%	$59.58	$59.58	$59.60	$59.60
Purchase #3	$17.44	4.564%	$18.236	$18.24	$18.25	$18.20
Purchase #4	$219.50	6.851%	$234.5379	$234.54	$234.55	$234.50
Purchase #5	$99.30	10.346%	$109.5736	$109.57	$109.55	$109.60
Purchase #6	$95.27	12.228%	$106.9196	$106.92	$106.90	$106.90
Purchase #7	$162.33	4.304%	$169.3167	$169.32	$169.30	$169.30
7 purchase totals =	$849.21		$926.4553	$926.46	$926.45	$926.40