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	$134.89	5.629%	$142.483	$142.48	$142.50	$142.50
Purchase #2	$176.59	6.769%	$188.5434	$188.54	$188.55	$188.50
Purchase #3	$190.57	13.638%	$216.5599	$216.56	$216.55	$216.60
Purchase #4	$225.77	7.456%	$242.6034	$242.60	$242.60	$242.60
Purchase #5	$6.79	7.402%	$7.2926	$7.29	$7.30	$7.30
Purchase #6	$30.79	11.793%	$34.4211	$34.42	$34.40	$34.40
Purchase #7	$205.63	3.156%	$212.1197	$212.12	$212.10	$212.10
7 purchase totals =	$971.03		$1,044.0231	$1,044.01	$1,044.00	$1,044.00