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	$46.84	12.323%	$52.6121	$52.61	$52.60	$52.60
Purchase #2	$38.37	8.336%	$41.5685	$41.57	$41.55	$41.60
Purchase #3	$54.28	10.199%	$59.816	$59.82	$59.80	$59.80
Purchase #4	$101.32	9.760%	$111.2088	$111.21	$111.20	$111.20
Purchase #5	$171.98	5.152%	$180.8404	$180.84	$180.85	$180.80
Purchase #6	$97.77	10.246%	$107.7875	$107.79	$107.80	$107.80
Purchase #7	$226.94	7.459%	$243.8675	$243.87	$243.85	$243.90
7 purchase totals =	$737.50		$797.7008	$797.71	$797.65	$797.70