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	$206.38	10.696%	$228.4544	$228.45	$228.45	$228.50
Purchase #2	$40.98	3.247%	$42.3106	$42.31	$42.30	$42.30
Purchase #3	$57.63	9.140%	$62.8974	$62.90	$62.90	$62.90
Purchase #4	$77.42	8.709%	$84.1625	$84.16	$84.15	$84.20
Purchase #5	$28.62	4.370%	$29.8707	$29.87	$29.85	$29.90
Purchase #6	$185.38	5.785%	$196.1042	$196.10	$196.10	$196.10
Purchase #7	$55.93	6.172%	$59.382	$59.38	$59.40	$59.40
7 purchase totals =	$652.34		$703.1818	$703.17	$703.15	$703.30