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	$89.31	6.688%	$95.2831	$95.28	$95.30	$95.30
Purchase #2	$155.70	7.462%	$167.3183	$167.32	$167.30	$167.30
Purchase #3	$39.66	7.293%	$42.5524	$42.55	$42.55	$42.60
Purchase #4	$106.97	13.731%	$121.6581	$121.66	$121.65	$121.70
Purchase #5	$71.27	12.310%	$80.0433	$80.04	$80.05	$80.00
Purchase #6	$162.38	3.830%	$168.5992	$168.60	$168.60	$168.60
Purchase #7	$101.63	7.805%	$109.5622	$109.56	$109.55	$109.60
7 purchase totals =	$726.92		$785.0166	$785.01	$785.00	$785.10