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	$159.34	6.184%	$169.1936	$169.19	$169.20	$169.20
Purchase #2	$26.59	8.685%	$28.8993	$28.90	$28.90	$28.90
Purchase #3	$198.33	12.378%	$222.8793	$222.88	$222.90	$222.90
Purchase #4	$51.64	4.299%	$53.86	$53.86	$53.85	$53.90
Purchase #5	$60.28	8.670%	$65.5063	$65.51	$65.50	$65.50
Purchase #6	$134.78	3.659%	$139.7116	$139.71	$139.70	$139.70
Purchase #7	$98.35	3.705%	$101.9939	$101.99	$102.00	$102.00
7 purchase totals =	$729.31		$782.0440	$782.04	$782.05	$782.10