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	$167.46	4.819%	$175.5299	$175.53	$175.55	$175.50
Purchase #2	$243.45	6.229%	$258.6145	$258.61	$258.60	$258.60
Purchase #3	$243.79	13.235%	$276.0556	$276.06	$276.05	$276.10
Purchase #4	$239.97	8.489%	$260.3411	$260.34	$260.35	$260.30
Purchase #5	$32.33	11.540%	$36.0609	$36.06	$36.05	$36.10
Purchase #6	$87.98	13.494%	$99.852	$99.85	$99.85	$99.90
Purchase #7	$118.47	7.466%	$127.315	$127.32	$127.30	$127.30
7 purchase totals =	$1,133.45		$1,233.7690	$1,233.77	$1,233.75	$1,233.80