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	$116.93	9.417%	$127.9413	$127.94	$127.95	$127.90
Purchase #2	$238.73	12.565%	$268.7264	$268.73	$268.75	$268.70
Purchase #3	$130.34	10.254%	$143.7051	$143.71	$143.70	$143.70
Purchase #4	$196.69	7.397%	$211.2392	$211.24	$211.25	$211.20
Purchase #5	$177.48	10.743%	$196.5467	$196.55	$196.55	$196.50
Purchase #6	$82.88	13.237%	$93.8508	$93.85	$93.85	$93.90
Purchase #7	$61.74	7.158%	$66.1593	$66.16	$66.15	$66.20
7 purchase totals =	$1,004.79		$1,108.1688	$1,108.18	$1,108.20	$1,108.10