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	$120.94	10.472%	$133.6048	$133.60	$133.60	$133.60
Purchase #2	$239.45	12.700%	$269.8602	$269.86	$269.85	$269.90
Purchase #3	$72.66	11.127%	$80.7449	$80.74	$80.75	$80.70
Purchase #4	$89.40	12.625%	$100.6868	$100.69	$100.70	$100.70
Purchase #5	$141.28	12.314%	$158.6772	$158.68	$158.70	$158.70
Purchase #6	$42.25	4.868%	$44.3067	$44.31	$44.30	$44.30
Purchase #7	$216.77	12.394%	$243.6365	$243.64	$243.65	$243.60
7 purchase totals =	$922.75		$1,031.5171	$1,031.52	$1,031.55	$1,031.50