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	$140.25	13.118%	$158.648	$158.65	$158.65	$158.60
Purchase #2	$88.97	11.829%	$99.4943	$99.49	$99.50	$99.50
Purchase #3	$72.44	7.506%	$77.8773	$77.88	$77.90	$77.90
Purchase #4	$167.67	12.646%	$188.8735	$188.87	$188.85	$188.90
Purchase #5	$52.53	12.707%	$59.205	$59.21	$59.20	$59.20
Purchase #6	$248.48	5.108%	$261.1724	$261.17	$261.15	$261.20
Purchase #7	$241.40	6.788%	$257.7862	$257.79	$257.80	$257.80
7 purchase totals =	$1,011.74		$1,103.0567	$1,103.06	$1,103.05	$1,103.10