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	$212.86	5.622%	$224.827	$224.83	$224.85	$224.80
Purchase #2	$191.97	4.663%	$200.9216	$200.92	$200.90	$200.90
Purchase #3	$235.55	5.739%	$249.0682	$249.07	$249.05	$249.10
Purchase #4	$39.86	13.697%	$45.3196	$45.32	$45.30	$45.30
Purchase #5	$96.87	13.473%	$109.9213	$109.92	$109.90	$109.90
Purchase #6	$96.77	6.718%	$103.271	$103.27	$103.25	$103.30
Purchase #7	$133.83	11.451%	$149.1549	$149.15	$149.15	$149.20
7 purchase totals =	$1,007.71		$1,082.4836	$1,082.48	$1,082.40	$1,082.50