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	$153.96	7.260%	$165.1375	$165.14	$165.15	$165.10
Purchase #2	$102.33	13.507%	$116.1517	$116.15	$116.15	$116.20
Purchase #3	$40.68	4.684%	$42.5855	$42.59	$42.60	$42.60
Purchase #4	$54.87	8.461%	$59.5126	$59.51	$59.50	$59.50
Purchase #5	$167.71	11.364%	$186.7686	$186.77	$186.75	$186.80
Purchase #6	$124.88	12.108%	$140.0005	$140.00	$140.00	$140.00
Purchase #7	$23.35	3.285%	$24.117	$24.12	$24.10	$24.10
7 purchase totals =	$667.78		$734.2734	$734.28	$734.25	$734.30