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	$234.93	12.316%	$263.864	$263.86	$263.85	$263.90
Purchase #2	$75.46	6.440%	$80.3196	$80.32	$80.30	$80.30
Purchase #3	$171.30	11.780%	$191.4791	$191.48	$191.50	$191.50
Purchase #4	$141.29	4.544%	$147.7102	$147.71	$147.70	$147.70
Purchase #5	$78.31	5.127%	$82.325	$82.33	$82.35	$82.30
Purchase #6	$152.68	12.274%	$171.4199	$171.42	$171.40	$171.40
Purchase #7	$158.41	11.413%	$176.4893	$176.49	$176.50	$176.50
7 purchase totals =	$1,012.38		$1,113.6071	$1,113.61	$1,113.60	$1,113.60