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	$200.51	11.177%	$222.921	$222.92	$222.90	$222.90
Purchase #2	$111.95	10.501%	$123.7059	$123.71	$123.70	$123.70
Purchase #3	$181.71	10.412%	$200.6296	$200.63	$200.65	$200.60
Purchase #4	$67.68	7.334%	$72.6437	$72.64	$72.65	$72.60
Purchase #5	$124.98	5.663%	$132.0576	$132.06	$132.05	$132.10
Purchase #6	$128.49	8.687%	$139.6519	$139.65	$139.65	$139.70
Purchase #7	$121.44	11.483%	$135.385	$135.39	$135.40	$135.40
7 purchase totals =	$936.76		$1,026.9947	$1,027.00	$1,027.00	$1,027.00