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	$219.46	4.481%	$229.294	$229.29	$229.30	$229.30
Purchase #2	$39.90	3.682%	$41.3691	$41.37	$41.35	$41.40
Purchase #3	$205.80	11.463%	$229.3909	$229.39	$229.40	$229.40
Purchase #4	$154.85	7.484%	$166.439	$166.44	$166.45	$166.40
Purchase #5	$195.94	9.381%	$214.3211	$214.32	$214.30	$214.30
Purchase #6	$245.81	7.390%	$263.9754	$263.98	$264.00	$264.00
Purchase #7	$150.45	3.676%	$155.9805	$155.98	$156.00	$156.00
7 purchase totals =	$1,212.21		$1,300.7700	$1,300.77	$1,300.80	$1,300.80