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	$101.40	3.613%	$105.0636	$105.06	$105.05	$105.10
Purchase #2	$12.86	3.734%	$13.3402	$13.34	$13.35	$13.30
Purchase #3	$74.63	7.358%	$80.1213	$80.12	$80.10	$80.10
Purchase #4	$106.40	10.640%	$117.721	$117.72	$117.70	$117.70
Purchase #5	$82.50	6.192%	$87.6084	$87.61	$87.60	$87.60
Purchase #6	$96.38	9.152%	$105.2007	$105.20	$105.20	$105.20
Purchase #7	$31.46	3.260%	$32.4856	$32.49	$32.50	$32.50
7 purchase totals =	$505.63		$541.5408	$541.54	$541.50	$541.50