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	$243.51	7.631%	$262.0922	$262.09	$262.10	$262.10
Purchase #2	$120.43	11.364%	$134.1157	$134.12	$134.10	$134.10
Purchase #3	$25.32	12.710%	$28.5382	$28.54	$28.55	$28.50
Purchase #4	$42.42	3.519%	$43.9128	$43.91	$43.90	$43.90
Purchase #5	$99.41	6.579%	$105.9502	$105.95	$105.95	$106.00
Purchase #6	$155.32	7.270%	$166.6118	$166.61	$166.60	$166.60
Purchase #7	$45.91	9.181%	$50.125	$50.13	$50.15	$50.10
7 purchase totals =	$732.32		$791.3459	$791.35	$791.35	$791.30