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	$189.75	5.331%	$199.8656	$199.87	$199.85	$199.90
Purchase #2	$67.52	7.712%	$72.7271	$72.73	$72.75	$72.70
Purchase #3	$160.70	5.368%	$169.3264	$169.33	$169.35	$169.30
Purchase #4	$230.37	12.678%	$259.5763	$259.58	$259.60	$259.60
Purchase #5	$9.41	9.283%	$10.2835	$10.28	$10.30	$10.30
Purchase #6	$77.75	10.143%	$85.6362	$85.64	$85.65	$85.60
Purchase #7	$211.59	5.158%	$222.5038	$222.50	$222.50	$222.50
7 purchase totals =	$947.09		$1,019.9189	$1,019.93	$1,020.00	$1,019.90