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	$141.32	4.195%	$147.2484	$147.25	$147.25	$147.20
Purchase #2	$100.54	11.802%	$112.4057	$112.41	$112.40	$112.40
Purchase #3	$101.69	9.553%	$111.4044	$111.40	$111.40	$111.40
Purchase #4	$166.56	13.408%	$188.8924	$188.89	$188.90	$188.90
Purchase #5	$162.58	3.768%	$168.706	$168.71	$168.70	$168.70
Purchase #6	$198.92	5.432%	$209.7253	$209.73	$209.75	$209.70
Purchase #7	$164.37	4.175%	$171.2324	$171.23	$171.25	$171.20
7 purchase totals =	$1,035.98		$1,109.6146	$1,109.62	$1,109.65	$1,109.50