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	$99.56	5.756%	$105.2907	$105.29	$105.30	$105.30
Purchase #2	$218.82	9.524%	$239.6604	$239.66	$239.65	$239.70
Purchase #3	$31.62	12.277%	$35.502	$35.50	$35.50	$35.50
Purchase #4	$50.97	3.647%	$52.8289	$52.83	$52.85	$52.80
Purchase #5	$223.89	8.782%	$243.552	$243.55	$243.55	$243.60
Purchase #6	$99.59	3.111%	$102.6882	$102.69	$102.70	$102.70
Purchase #7	$187.69	3.867%	$194.948	$194.95	$194.95	$194.90
7 purchase totals =	$912.14		$974.4702	$974.47	$974.50	$974.50