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	$91.68	8.133%	$99.1363	$99.14	$99.15	$99.10
Purchase #2	$151.56	8.455%	$164.3744	$164.37	$164.35	$164.40
Purchase #3	$160.88	3.114%	$165.8898	$165.89	$165.90	$165.90
Purchase #4	$172.59	8.107%	$186.5819	$186.58	$186.60	$186.60
Purchase #5	$223.76	4.826%	$234.5587	$234.56	$234.55	$234.60
Purchase #6	$188.29	9.468%	$206.1173	$206.12	$206.10	$206.10
Purchase #7	$43.36	5.719%	$45.8398	$45.84	$45.85	$45.80
7 purchase totals =	$1,032.12		$1,102.4982	$1,102.50	$1,102.50	$1,102.50