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	$151.49	4.310%	$158.0192	$158.02	$158.00	$158.00
Purchase #2	$121.26	11.676%	$135.4183	$135.42	$135.40	$135.40
Purchase #3	$232.73	4.211%	$242.5303	$242.53	$242.55	$242.50
Purchase #4	$90.61	9.577%	$99.2877	$99.29	$99.30	$99.30
Purchase #5	$105.82	7.618%	$113.8814	$113.88	$113.90	$113.90
Purchase #6	$243.68	7.250%	$261.3468	$261.35	$261.35	$261.30
Purchase #7	$92.72	6.646%	$98.8822	$98.88	$98.90	$98.90
7 purchase totals =	$1,038.31		$1,109.3659	$1,109.37	$1,109.40	$1,109.30