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	$162.76	7.531%	$175.0175	$175.02	$175.00	$175.00
Purchase #2	$26.80	9.372%	$29.3117	$29.31	$29.30	$29.30
Purchase #3	$176.57	11.216%	$196.3741	$196.37	$196.35	$196.40
Purchase #4	$250.64	6.721%	$267.4855	$267.49	$267.50	$267.50
Purchase #5	$33.77	10.663%	$37.3709	$37.37	$37.35	$37.40
Purchase #6	$79.43	11.378%	$88.4675	$88.47	$88.45	$88.50
Purchase #7	$5.72	12.828%	$6.4538	$6.45	$6.45	$6.50
7 purchase totals =	$735.69		$800.4810	$800.48	$800.40	$800.60