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	$114.40	11.518%	$127.5766	$127.58	$127.60	$127.60
Purchase #2	$181.66	13.528%	$206.235	$206.24	$206.25	$206.20
Purchase #3	$79.64	11.272%	$88.617	$88.62	$88.60	$88.60
Purchase #4	$182.58	10.732%	$202.1745	$202.17	$202.15	$202.20
Purchase #5	$169.63	5.848%	$179.55	$179.55	$179.55	$179.60
Purchase #6	$37.41	4.347%	$39.0362	$39.04	$39.05	$39.00
Purchase #7	$209.72	6.240%	$222.8065	$222.81	$222.80	$222.80
7 purchase totals =	$975.04		$1,065.9958	$1,066.01	$1,066.00	$1,066.00