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	$71.66	7.116%	$76.7593	$76.76	$76.75	$76.80
Purchase #2	$90.52	8.539%	$98.2495	$98.25	$98.25	$98.20
Purchase #3	$241.51	8.215%	$261.35	$261.35	$261.35	$261.40
Purchase #4	$26.36	13.374%	$29.8854	$29.89	$29.90	$29.90
Purchase #5	$159.85	5.412%	$168.5011	$168.50	$168.50	$168.50
Purchase #6	$221.32	7.578%	$238.0916	$238.09	$238.10	$238.10
Purchase #7	$198.81	11.617%	$221.9058	$221.91	$221.90	$221.90
7 purchase totals =	$1,010.03		$1,094.7427	$1,094.75	$1,094.75	$1,094.80