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	$161.44	5.153%	$169.759	$169.76	$169.75	$169.80
Purchase #2	$162.70	5.385%	$171.4614	$171.46	$171.45	$171.50
Purchase #3	$204.93	5.718%	$216.6479	$216.65	$216.65	$216.60
Purchase #4	$37.59	13.777%	$42.7688	$42.77	$42.75	$42.80
Purchase #5	$79.94	7.526%	$85.9563	$85.96	$85.95	$86.00
Purchase #6	$136.86	11.670%	$152.8316	$152.83	$152.85	$152.80
Purchase #7	$105.98	5.192%	$111.4825	$111.48	$111.50	$111.50
7 purchase totals =	$889.44		$950.9075	$950.91	$950.90	$951.00