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	$138.34	7.751%	$149.0627	$149.06	$149.05	$149.10
Purchase #2	$78.63	5.415%	$82.8878	$82.89	$82.90	$82.90
Purchase #3	$19.49	3.347%	$20.1423	$20.14	$20.15	$20.10
Purchase #4	$83.83	7.743%	$90.321	$90.32	$90.30	$90.30
Purchase #5	$209.72	11.192%	$233.1919	$233.19	$233.20	$233.20
Purchase #6	$231.89	13.223%	$262.5528	$262.55	$262.55	$262.60
Purchase #7	$106.72	11.181%	$118.6524	$118.65	$118.65	$118.70
7 purchase totals =	$868.62		$956.8109	$956.80	$956.80	$956.90