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	$88.65	9.386%	$96.9707	$96.97	$96.95	$97.00
Purchase #2	$133.61	8.866%	$145.4559	$145.46	$145.45	$145.50
Purchase #3	$117.37	12.381%	$131.9016	$131.90	$131.90	$131.90
Purchase #4	$27.65	6.767%	$29.5211	$29.52	$29.50	$29.50
Purchase #5	$118.98	8.626%	$129.2432	$129.24	$129.25	$129.20
Purchase #6	$178.48	12.216%	$200.2831	$200.28	$200.30	$200.30
Purchase #7	$78.81	4.620%	$82.451	$82.45	$82.45	$82.50
7 purchase totals =	$743.55		$815.8266	$815.82	$815.80	$815.90