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	$204.71	5.670%	$216.3171	$216.32	$216.30	$216.30
Purchase #2	$53.32	12.391%	$59.9269	$59.93	$59.95	$59.90
Purchase #3	$7.46	3.353%	$7.7101	$7.71	$7.70	$7.70
Purchase #4	$101.55	9.229%	$110.922	$110.92	$110.90	$110.90
Purchase #5	$166.31	10.791%	$184.2565	$184.26	$184.25	$184.30
Purchase #6	$108.87	10.184%	$119.9573	$119.96	$119.95	$120.00
Purchase #7	$135.71	8.600%	$147.3811	$147.38	$147.40	$147.40
7 purchase totals =	$777.93		$846.4710	$846.48	$846.45	$846.50