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	$170.59	11.596%	$190.3716	$190.37	$190.35	$190.40
Purchase #2	$152.63	10.652%	$168.8881	$168.89	$168.90	$168.90
Purchase #3	$90.62	12.294%	$101.7608	$101.76	$101.75	$101.80
Purchase #4	$86.67	4.522%	$90.5892	$90.59	$90.60	$90.60
Purchase #5	$181.91	8.655%	$197.6543	$197.65	$197.65	$197.70
Purchase #6	$199.74	3.334%	$206.3993	$206.40	$206.40	$206.40
Purchase #7	$56.98	13.465%	$64.6524	$64.65	$64.65	$64.70
7 purchase totals =	$939.14		$1,020.3157	$1,020.31	$1,020.30	$1,020.50