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	$95.62	3.725%	$99.1818	$99.18	$99.20	$99.20
Purchase #2	$93.84	8.632%	$101.9403	$101.94	$101.95	$101.90
Purchase #3	$191.94	4.293%	$200.18	$200.18	$200.20	$200.20
Purchase #4	$249.32	4.618%	$260.8336	$260.83	$260.85	$260.80
Purchase #5	$40.54	12.367%	$45.5536	$45.55	$45.55	$45.60
Purchase #6	$11.50	4.859%	$12.0588	$12.06	$12.05	$12.10
Purchase #7	$25.41	11.740%	$28.3931	$28.39	$28.40	$28.40
7 purchase totals =	$708.17		$748.1412	$748.13	$748.20	$748.20