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	$59.26	4.810%	$62.1104	$62.11	$62.10	$62.10
Purchase #2	$85.31	5.204%	$89.7495	$89.75	$89.75	$89.70
Purchase #3	$128.29	5.409%	$135.2292	$135.23	$135.25	$135.20
Purchase #4	$37.95	10.807%	$42.0513	$42.05	$42.05	$42.10
Purchase #5	$91.36	13.235%	$103.4515	$103.45	$103.45	$103.50
Purchase #6	$37.28	3.110%	$38.4394	$38.44	$38.45	$38.40
Purchase #7	$104.45	11.476%	$116.4367	$116.44	$116.45	$116.40
7 purchase totals =	$543.90		$587.4680	$587.47	$587.50	$587.40