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	$95.61	4.704%	$100.1075	$100.11	$100.10	$100.10
Purchase #2	$127.29	9.501%	$139.3838	$139.38	$139.40	$139.40
Purchase #3	$139.78	5.306%	$147.1967	$147.20	$147.20	$147.20
Purchase #4	$52.27	5.447%	$55.1171	$55.12	$55.10	$55.10
Purchase #5	$45.95	11.647%	$51.3018	$51.30	$51.30	$51.30
Purchase #6	$144.39	13.576%	$163.9924	$163.99	$164.00	$164.00
Purchase #7	$70.47	11.497%	$78.5719	$78.57	$78.55	$78.60
7 purchase totals =	$675.76		$735.6712	$735.67	$735.65	$735.70