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	$100.46	8.827%	$109.3276	$109.33	$109.35	$109.30
Purchase #2	$7.25	8.454%	$7.8629	$7.86	$7.85	$7.90
Purchase #3	$49.78	4.662%	$52.1007	$52.10	$52.10	$52.10
Purchase #4	$189.76	3.291%	$196.005	$196.01	$196.00	$196.00
Purchase #5	$185.72	9.324%	$203.0365	$203.04	$203.05	$203.00
Purchase #6	$200.61	13.186%	$227.0624	$227.06	$227.05	$227.10
Purchase #7	$107.53	9.196%	$117.4185	$117.42	$117.40	$117.40
7 purchase totals =	$841.11		$912.8136	$912.82	$912.80	$912.80