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	$126.95	3.826%	$131.8071	$131.81	$131.80	$131.80
Purchase #2	$91.98	8.825%	$100.0972	$100.10	$100.10	$100.10
Purchase #3	$59.84	6.871%	$63.9516	$63.95	$63.95	$64.00
Purchase #4	$68.98	3.809%	$71.6074	$71.61	$71.60	$71.60
Purchase #5	$114.32	11.506%	$127.4737	$127.47	$127.45	$127.50
Purchase #6	$198.58	5.398%	$209.2993	$209.30	$209.30	$209.30
Purchase #7	$181.45	7.226%	$194.5616	$194.56	$194.55	$194.60
7 purchase totals =	$842.10		$898.7979	$898.80	$898.75	$898.90