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	$90.31	6.774%	$96.4276	$96.43	$96.45	$96.40
Purchase #2	$54.26	4.453%	$56.6762	$56.68	$56.70	$56.70
Purchase #3	$18.50	4.589%	$19.349	$19.35	$19.35	$19.30
Purchase #4	$84.81	6.742%	$90.5279	$90.53	$90.55	$90.50
Purchase #5	$180.61	4.546%	$188.8205	$188.82	$188.80	$188.80
Purchase #6	$57.73	3.761%	$59.9012	$59.90	$59.90	$59.90
Purchase #7	$196.89	5.222%	$207.1716	$207.17	$207.15	$207.20
7 purchase totals =	$683.11		$718.8740	$718.88	$718.90	$718.80