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	$57.60	7.125%	$61.704	$61.70	$61.70	$61.70
Purchase #2	$83.25	8.544%	$90.3629	$90.36	$90.35	$90.40
Purchase #3	$98.51	12.263%	$110.5903	$110.59	$110.60	$110.60
Purchase #4	$156.32	7.573%	$168.1581	$168.16	$168.15	$168.20
Purchase #5	$248.66	5.380%	$262.0379	$262.04	$262.05	$262.00
Purchase #6	$168.51	3.376%	$174.1989	$174.20	$174.20	$174.20
Purchase #7	$195.89	8.846%	$213.2184	$213.22	$213.20	$213.20
7 purchase totals =	$1,008.74		$1,080.2705	$1,080.27	$1,080.25	$1,080.30