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	$127.59	4.851%	$133.7794	$133.78	$133.80	$133.80
Purchase #2	$35.89	5.666%	$37.9235	$37.92	$37.90	$37.90
Purchase #3	$57.82	5.834%	$61.1932	$61.19	$61.20	$61.20
Purchase #4	$239.31	9.819%	$262.8078	$262.81	$262.80	$262.80
Purchase #5	$109.98	6.273%	$116.879	$116.88	$116.90	$116.90
Purchase #6	$124.75	11.658%	$139.2934	$139.29	$139.30	$139.30
Purchase #7	$203.84	8.288%	$220.7343	$220.73	$220.75	$220.70
7 purchase totals =	$899.18		$972.6106	$972.60	$972.65	$972.60