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	$157.59	7.522%	$169.4439	$169.44	$169.45	$169.40
Purchase #2	$52.61	12.781%	$59.3341	$59.33	$59.35	$59.30
Purchase #3	$229.35	11.735%	$256.2642	$256.26	$256.25	$256.30
Purchase #4	$172.94	10.449%	$191.0105	$191.01	$191.00	$191.00
Purchase #5	$53.62	13.346%	$60.7761	$60.78	$60.80	$60.80
Purchase #6	$245.87	11.242%	$273.5107	$273.51	$273.50	$273.50
Purchase #7	$154.26	11.247%	$171.6096	$171.61	$171.60	$171.60
7 purchase totals =	$1,066.24		$1,181.9491	$1,181.94	$1,181.95	$1,181.90