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	$89.62	10.761%	$99.264	$99.26	$99.25	$99.30
Purchase #2	$242.97	5.199%	$255.602	$255.60	$255.60	$255.60
Purchase #3	$108.98	12.172%	$122.245	$122.25	$122.25	$122.20
Purchase #4	$245.60	7.853%	$264.887	$264.89	$264.90	$264.90
Purchase #5	$118.64	6.316%	$126.1333	$126.13	$126.15	$126.10
Purchase #6	$112.75	9.358%	$123.3011	$123.30	$123.30	$123.30
Purchase #7	$190.71	7.415%	$204.8511	$204.85	$204.85	$204.90
7 purchase totals =	$1,109.27		$1,196.2835	$1,196.28	$1,196.30	$1,196.30