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	$218.84	12.281%	$245.7157	$245.72	$245.70	$245.70
Purchase #2	$82.45	3.333%	$85.1981	$85.20	$85.20	$85.20
Purchase #3	$28.34	13.119%	$32.0579	$32.06	$32.05	$32.10
Purchase #4	$191.39	8.416%	$207.4974	$207.50	$207.50	$207.50
Purchase #5	$134.90	4.836%	$141.4238	$141.42	$141.40	$141.40
Purchase #6	$56.60	4.864%	$59.353	$59.35	$59.35	$59.40
Purchase #7	$187.47	11.596%	$209.209	$209.21	$209.20	$209.20
7 purchase totals =	$899.99		$980.4549	$980.46	$980.40	$980.50