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	$210.45	11.766%	$235.2115	$235.21	$235.20	$235.20
Purchase #2	$80.28	11.699%	$89.672	$89.67	$89.65	$89.70
Purchase #3	$48.27	4.538%	$50.4605	$50.46	$50.45	$50.50
Purchase #4	$54.78	4.156%	$57.0567	$57.06	$57.05	$57.10
Purchase #5	$146.36	4.514%	$152.9667	$152.97	$152.95	$153.00
Purchase #6	$188.83	5.703%	$199.599	$199.60	$199.60	$199.60
Purchase #7	$86.98	6.678%	$92.7885	$92.79	$92.80	$92.80
7 purchase totals =	$815.95		$877.7549	$877.76	$877.70	$877.90