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	$138.69	6.722%	$148.0127	$148.01	$148.00	$148.00
Purchase #2	$33.34	8.356%	$36.1259	$36.13	$36.15	$36.10
Purchase #3	$35.78	5.376%	$37.7035	$37.70	$37.70	$37.70
Purchase #4	$100.73	3.630%	$104.3865	$104.39	$104.40	$104.40
Purchase #5	$50.83	12.486%	$57.1766	$57.18	$57.20	$57.20
Purchase #6	$72.86	12.688%	$82.1045	$82.10	$82.10	$82.10
Purchase #7	$89.76	11.591%	$100.1641	$100.16	$100.15	$100.20
7 purchase totals =	$521.99		$565.6738	$565.67	$565.70	$565.70