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	$164.32	6.798%	$175.4905	$175.49	$175.50	$175.50
Purchase #2	$110.59	4.476%	$115.54	$115.54	$115.55	$115.50
Purchase #3	$174.97	9.448%	$191.5012	$191.50	$191.50	$191.50
Purchase #4	$116.77	11.697%	$130.4286	$130.43	$130.45	$130.40
Purchase #5	$50.68	13.438%	$57.4904	$57.49	$57.50	$57.50
Purchase #6	$182.85	12.608%	$205.9037	$205.90	$205.90	$205.90
Purchase #7	$127.81	12.578%	$143.8859	$143.89	$143.90	$143.90
7 purchase totals =	$927.99		$1,020.2403	$1,020.24	$1,020.30	$1,020.20