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	$22.72	10.594%	$25.127	$25.13	$25.15	$25.10
Purchase #2	$130.27	13.874%	$148.3437	$148.34	$148.35	$148.30
Purchase #3	$57.68	3.723%	$59.8274	$59.83	$59.85	$59.80
Purchase #4	$41.62	5.853%	$44.056	$44.06	$44.05	$44.10
Purchase #5	$22.86	5.797%	$24.1852	$24.19	$24.20	$24.20
Purchase #6	$125.31	13.538%	$142.2745	$142.27	$142.25	$142.30
Purchase #7	$243.32	6.380%	$258.8438	$258.84	$258.85	$258.80
7 purchase totals =	$643.78		$702.6576	$702.66	$702.70	$702.60