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	$29.83	12.777%	$33.6414	$33.64	$33.65	$33.60
Purchase #2	$165.71	8.689%	$180.1085	$180.11	$180.10	$180.10
Purchase #3	$141.73	7.534%	$152.4079	$152.41	$152.40	$152.40
Purchase #4	$230.48	4.156%	$240.0587	$240.06	$240.05	$240.10
Purchase #5	$79.58	3.305%	$82.2101	$82.21	$82.20	$82.20
Purchase #6	$180.88	13.620%	$205.5159	$205.52	$205.50	$205.50
Purchase #7	$185.64	7.433%	$199.4386	$199.44	$199.45	$199.40
7 purchase totals =	$1,013.85		$1,093.3811	$1,093.39	$1,093.35	$1,093.30