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	$156.69	3.480%	$162.1428	$162.14	$162.15	$162.10
Purchase #2	$58.32	6.127%	$61.8933	$61.89	$61.90	$61.90
Purchase #3	$72.73	13.832%	$82.79	$82.79	$82.80	$82.80
Purchase #4	$8.68	11.855%	$9.709	$9.71	$9.70	$9.70
Purchase #5	$104.47	8.288%	$113.1285	$113.13	$113.15	$113.10
Purchase #6	$50.29	11.152%	$55.8983	$55.90	$55.90	$55.90
Purchase #7	$129.49	12.807%	$146.0738	$146.07	$146.05	$146.10
7 purchase totals =	$580.67		$631.6357	$631.63	$631.65	$631.60