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	$31.32	10.461%	$34.5964	$34.60	$34.60	$34.60
Purchase #2	$73.54	7.837%	$79.3033	$79.30	$79.30	$79.30
Purchase #3	$45.84	6.693%	$48.9081	$48.91	$48.90	$48.90
Purchase #4	$51.41	12.182%	$57.6728	$57.67	$57.65	$57.70
Purchase #5	$142.82	11.112%	$158.6902	$158.69	$158.70	$158.70
Purchase #6	$54.85	7.857%	$59.1596	$59.16	$59.15	$59.20
Purchase #7	$188.91	3.679%	$195.86	$195.86	$195.85	$195.90
7 purchase totals =	$588.69		$634.1904	$634.19	$634.15	$634.30