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	$222.68	12.216%	$249.8826	$249.88	$249.90	$249.90
Purchase #2	$25.80	10.460%	$28.4987	$28.50	$28.50	$28.50
Purchase #3	$42.35	9.630%	$46.4283	$46.43	$46.45	$46.40
Purchase #4	$218.54	12.136%	$245.062	$245.06	$245.05	$245.10
Purchase #5	$223.85	6.508%	$238.4182	$238.42	$238.40	$238.40
Purchase #6	$142.29	13.814%	$161.9459	$161.95	$161.95	$161.90
Purchase #7	$37.35	12.762%	$42.1166	$42.12	$42.10	$42.10
7 purchase totals =	$912.86		$1,012.3523	$1,012.36	$1,012.35	$1,012.30