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	$43.86	3.232%	$45.2776	$45.28	$45.30	$45.30
Purchase #2	$127.52	5.395%	$134.3997	$134.40	$134.40	$134.40
Purchase #3	$212.91	5.426%	$224.4625	$224.46	$224.45	$224.50
Purchase #4	$53.48	7.732%	$57.6151	$57.62	$57.60	$57.60
Purchase #5	$17.31	9.204%	$18.9032	$18.90	$18.90	$18.90
Purchase #6	$201.39	7.529%	$216.5527	$216.55	$216.55	$216.60
Purchase #7	$143.41	10.751%	$158.828	$158.83	$158.85	$158.80
7 purchase totals =	$799.88		$856.0388	$856.04	$856.05	$856.10