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	$117.94	13.852%	$134.277	$134.28	$134.30	$134.30
Purchase #2	$185.63	3.252%	$191.6667	$191.67	$191.65	$191.70
Purchase #3	$115.36	10.404%	$127.3621	$127.36	$127.35	$127.40
Purchase #4	$239.45	3.261%	$247.2585	$247.26	$247.25	$247.30
Purchase #5	$170.65	12.203%	$191.4744	$191.47	$191.45	$191.50
Purchase #6	$82.88	8.193%	$89.6704	$89.67	$89.65	$89.70
Purchase #7	$77.96	3.392%	$80.6044	$80.60	$80.60	$80.60
7 purchase totals =	$989.87		$1,062.3135	$1,062.31	$1,062.25	$1,062.50