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	$32.46	5.297%	$34.1794	$34.18	$34.20	$34.20
Purchase #2	$109.57	12.488%	$123.2531	$123.25	$123.25	$123.30
Purchase #3	$195.29	13.365%	$221.3905	$221.39	$221.40	$221.40
Purchase #4	$213.28	6.477%	$227.0941	$227.09	$227.10	$227.10
Purchase #5	$102.48	4.385%	$106.9737	$106.97	$106.95	$107.00
Purchase #6	$99.31	11.151%	$110.3841	$110.38	$110.40	$110.40
Purchase #7	$171.43	10.107%	$188.7564	$188.76	$188.75	$188.80
7 purchase totals =	$923.82		$1,012.0313	$1,012.02	$1,012.05	$1,012.20