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	$99.94	5.280%	$105.2168	$105.22	$105.20	$105.20
Purchase #2	$207.49	7.852%	$223.7821	$223.78	$223.80	$223.80
Purchase #3	$18.70	4.111%	$19.4688	$19.47	$19.45	$19.50
Purchase #4	$43.51	6.571%	$46.369	$46.37	$46.35	$46.40
Purchase #5	$53.96	6.629%	$57.537	$57.54	$57.55	$57.50
Purchase #6	$45.98	3.530%	$47.6031	$47.60	$47.60	$47.60
Purchase #7	$179.29	7.394%	$192.5467	$192.55	$192.55	$192.50
7 purchase totals =	$648.87		$692.5235	$692.53	$692.50	$692.50