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	$175.77	11.677%	$196.2947	$196.29	$196.30	$196.30
Purchase #2	$224.38	9.351%	$245.3618	$245.36	$245.35	$245.40
Purchase #3	$69.85	3.152%	$72.0517	$72.05	$72.05	$72.10
Purchase #4	$33.84	5.637%	$35.7476	$35.75	$35.75	$35.70
Purchase #5	$243.78	3.668%	$252.7219	$252.72	$252.70	$252.70
Purchase #6	$51.57	4.120%	$53.6947	$53.69	$53.70	$53.70
Purchase #7	$114.27	4.582%	$119.5059	$119.51	$119.50	$119.50
7 purchase totals =	$913.46		$975.3783	$975.37	$975.35	$975.40