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	$98.70	3.526%	$102.1802	$102.18	$102.20	$102.20
Purchase #2	$18.33	5.255%	$19.2932	$19.29	$19.30	$19.30
Purchase #3	$111.44	5.198%	$117.2327	$117.23	$117.25	$117.20
Purchase #4	$78.33	10.542%	$86.5875	$86.59	$86.60	$86.60
Purchase #5	$82.29	7.327%	$88.3194	$88.32	$88.30	$88.30
Purchase #6	$89.83	9.704%	$98.5471	$98.55	$98.55	$98.50
Purchase #7	$90.47	5.135%	$95.1156	$95.12	$95.10	$95.10
7 purchase totals =	$569.39		$607.2757	$607.28	$607.30	$607.20