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	$41.56	10.711%	$46.0115	$46.01	$46.00	$46.00
Purchase #2	$225.98	3.476%	$233.8351	$233.84	$233.85	$233.80
Purchase #3	$91.32	13.550%	$103.6939	$103.69	$103.70	$103.70
Purchase #4	$219.78	13.327%	$249.0701	$249.07	$249.05	$249.10
Purchase #5	$106.37	4.468%	$111.1226	$111.12	$111.10	$111.10
Purchase #6	$120.45	9.242%	$131.582	$131.58	$131.60	$131.60
Purchase #7	$40.46	3.150%	$41.7345	$41.73	$41.75	$41.70
7 purchase totals =	$845.92		$917.0497	$917.04	$917.05	$917.00