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	$105.74	4.693%	$110.7024	$110.70	$110.70	$110.70
Purchase #2	$78.90	13.349%	$89.4324	$89.43	$89.45	$89.40
Purchase #3	$87.64	13.825%	$99.7562	$99.76	$99.75	$99.80
Purchase #4	$76.89	3.256%	$79.3935	$79.39	$79.40	$79.40
Purchase #5	$82.46	11.394%	$91.8555	$91.86	$91.85	$91.90
Purchase #6	$138.82	12.169%	$155.713	$155.71	$155.70	$155.70
Purchase #7	$19.70	8.206%	$21.3166	$21.32	$21.30	$21.30
7 purchase totals =	$590.15		$648.1696	$648.17	$648.15	$648.20