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	$134.69	10.571%	$148.9281	$148.93	$148.95	$148.90
Purchase #2	$124.53	3.376%	$128.7341	$128.73	$128.75	$128.70
Purchase #3	$133.27	13.492%	$151.2508	$151.25	$151.25	$151.30
Purchase #4	$90.33	11.326%	$100.5608	$100.56	$100.55	$100.60
Purchase #5	$236.37	12.189%	$265.1811	$265.18	$265.20	$265.20
Purchase #6	$5.58	13.633%	$6.3407	$6.34	$6.35	$6.30
Purchase #7	$74.56	11.187%	$82.901	$82.90	$82.90	$82.90
7 purchase totals =	$799.33		$883.8966	$883.89	$883.95	$883.90