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	$189.40	13.391%	$214.7626	$214.76	$214.75	$214.80
Purchase #2	$67.80	5.656%	$71.6348	$71.63	$71.65	$71.60
Purchase #3	$56.89	6.383%	$60.5213	$60.52	$60.50	$60.50
Purchase #4	$84.89	13.139%	$96.0437	$96.04	$96.05	$96.00
Purchase #5	$34.83	9.412%	$38.1082	$38.11	$38.10	$38.10
Purchase #6	$95.36	9.856%	$104.7587	$104.76	$104.75	$104.80
Purchase #7	$113.63	5.526%	$119.9092	$119.91	$119.90	$119.90
7 purchase totals =	$642.80		$705.7385	$705.73	$705.70	$705.70