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	$55.73	11.791%	$62.3011	$62.30	$62.30	$62.30
Purchase #2	$180.61	4.464%	$188.6724	$188.67	$188.65	$188.70
Purchase #3	$72.77	7.654%	$78.3398	$78.34	$78.35	$78.30
Purchase #4	$243.74	12.326%	$273.7834	$273.78	$273.80	$273.80
Purchase #5	$167.64	13.696%	$190.6	$190.60	$190.60	$190.60
Purchase #6	$199.87	9.241%	$218.34	$218.34	$218.35	$218.30
Purchase #7	$200.29	8.366%	$217.0463	$217.05	$217.05	$217.00
7 purchase totals =	$1,120.65		$1,229.0830	$1,229.08	$1,229.10	$1,229.00