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	$201.29	4.467%	$210.2816	$210.28	$210.30	$210.30
Purchase #2	$234.65	9.812%	$257.6739	$257.67	$257.65	$257.70
Purchase #3	$143.47	7.694%	$154.5086	$154.51	$154.50	$154.50
Purchase #4	$194.87	10.621%	$215.5671	$215.57	$215.55	$215.60
Purchase #5	$56.55	4.289%	$58.9754	$58.98	$59.00	$59.00
Purchase #6	$83.30	7.424%	$89.4842	$89.48	$89.50	$89.50
Purchase #7	$48.53	7.227%	$52.0373	$52.04	$52.05	$52.00
7 purchase totals =	$962.66		$1,038.5281	$1,038.53	$1,038.55	$1,038.60