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	$105.43	13.688%	$119.8613	$119.86	$119.85	$119.90
Purchase #2	$184.88	3.692%	$191.7058	$191.71	$191.70	$191.70
Purchase #3	$206.61	4.266%	$215.424	$215.42	$215.40	$215.40
Purchase #4	$62.61	3.351%	$64.7081	$64.71	$64.70	$64.70
Purchase #5	$91.89	4.738%	$96.2437	$96.24	$96.25	$96.20
Purchase #6	$73.29	12.770%	$82.6491	$82.65	$82.65	$82.60
Purchase #7	$165.70	8.180%	$179.2543	$179.25	$179.25	$179.30
7 purchase totals =	$890.41		$949.8463	$949.84	$949.80	$949.80