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	$96.97	7.331%	$104.0789	$104.08	$104.10	$104.10
Purchase #2	$74.83	3.128%	$77.1707	$77.17	$77.15	$77.20
Purchase #3	$212.65	4.649%	$222.5361	$222.54	$222.55	$222.50
Purchase #4	$12.60	9.321%	$13.7744	$13.77	$13.75	$13.80
Purchase #5	$250.48	5.619%	$264.5545	$264.55	$264.55	$264.60
Purchase #6	$227.89	9.542%	$249.6353	$249.64	$249.65	$249.60
Purchase #7	$9.96	5.295%	$10.4874	$10.49	$10.50	$10.50
7 purchase totals =	$885.38		$942.2373	$942.24	$942.25	$942.30