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	$130.61	8.583%	$141.8203	$141.82	$141.80	$141.80
Purchase #2	$181.60	8.217%	$196.5221	$196.52	$196.50	$196.50
Purchase #3	$230.35	8.154%	$249.1327	$249.13	$249.15	$249.10
Purchase #4	$74.27	3.430%	$76.8175	$76.82	$76.80	$76.80
Purchase #5	$192.74	6.829%	$205.9022	$205.90	$205.90	$205.90
Purchase #6	$110.78	4.260%	$115.4992	$115.50	$115.50	$115.50
Purchase #7	$145.36	9.594%	$159.3058	$159.31	$159.30	$159.30
7 purchase totals =	$1,065.71		$1,144.9998	$1,145.00	$1,144.95	$1,144.90