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	$226.39	10.593%	$250.3715	$250.37	$250.35	$250.40
Purchase #2	$160.89	3.348%	$166.2766	$166.28	$166.30	$166.30
Purchase #3	$27.27	3.482%	$28.2195	$28.22	$28.20	$28.20
Purchase #4	$45.93	4.338%	$47.9224	$47.92	$47.90	$47.90
Purchase #5	$157.86	12.480%	$177.5609	$177.56	$177.55	$177.60
Purchase #6	$59.52	4.830%	$62.3948	$62.39	$62.40	$62.40
Purchase #7	$246.46	9.533%	$269.955	$269.96	$269.95	$270.00
7 purchase totals =	$924.32		$1,002.7007	$1,002.70	$1,002.65	$1,002.80