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	$187.66	4.650%	$196.3862	$196.39	$196.40	$196.40
Purchase #2	$104.31	9.558%	$114.2799	$114.28	$114.30	$114.30
Purchase #3	$130.49	11.550%	$145.5616	$145.56	$145.55	$145.60
Purchase #4	$227.90	9.483%	$249.5118	$249.51	$249.50	$249.50
Purchase #5	$111.83	4.666%	$117.048	$117.05	$117.05	$117.00
Purchase #6	$10.85	9.579%	$11.8893	$11.89	$11.90	$11.90
Purchase #7	$218.95	13.519%	$248.5499	$248.55	$248.55	$248.50
7 purchase totals =	$991.99		$1,083.2267	$1,083.23	$1,083.25	$1,083.20