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	$98.36	11.722%	$109.8898	$109.89	$109.90	$109.90
Purchase #2	$80.46	3.294%	$83.1104	$83.11	$83.10	$83.10
Purchase #3	$182.86	4.232%	$190.5986	$190.60	$190.60	$190.60
Purchase #4	$93.63	5.176%	$98.4763	$98.48	$98.50	$98.50
Purchase #5	$7.95	8.789%	$8.6487	$8.65	$8.65	$8.60
Purchase #6	$37.77	8.805%	$41.0956	$41.10	$41.10	$41.10
Purchase #7	$192.42	4.157%	$200.4189	$200.42	$200.40	$200.40
7 purchase totals =	$693.45		$732.2383	$732.25	$732.25	$732.20