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	$130.59	9.601%	$143.1279	$143.13	$143.15	$143.10
Purchase #2	$26.75	7.701%	$28.81	$28.81	$28.80	$28.80
Purchase #3	$122.60	7.577%	$131.8894	$131.89	$131.90	$131.90
Purchase #4	$22.61	10.799%	$25.0517	$25.05	$25.05	$25.10
Purchase #5	$156.34	9.752%	$171.5863	$171.59	$171.60	$171.60
Purchase #6	$142.98	9.648%	$156.7747	$156.77	$156.75	$156.80
Purchase #7	$127.86	5.469%	$134.8527	$134.85	$134.85	$134.90
7 purchase totals =	$729.73		$792.0927	$792.09	$792.10	$792.20