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	$50.35	13.396%	$57.0949	$57.09	$57.10	$57.10
Purchase #2	$14.28	5.478%	$15.0623	$15.06	$15.05	$15.10
Purchase #3	$12.73	10.215%	$14.0304	$14.03	$14.05	$14.00
Purchase #4	$98.62	10.644%	$109.1171	$109.12	$109.10	$109.10
Purchase #5	$42.37	6.667%	$45.1948	$45.19	$45.20	$45.20
Purchase #6	$105.40	12.857%	$118.9513	$118.95	$118.95	$119.00
Purchase #7	$227.63	6.499%	$242.4237	$242.42	$242.40	$242.40
7 purchase totals =	$551.38		$601.8745	$601.86	$601.85	$601.90