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	$189.66	3.806%	$196.8785	$196.88	$196.90	$196.90
Purchase #2	$225.76	6.661%	$240.7979	$240.80	$240.80	$240.80
Purchase #3	$17.82	9.845%	$19.5744	$19.57	$19.55	$19.60
Purchase #4	$72.88	10.207%	$80.3189	$80.32	$80.30	$80.30
Purchase #5	$202.44	3.544%	$209.6145	$209.61	$209.60	$209.60
Purchase #6	$218.25	12.410%	$245.3348	$245.33	$245.35	$245.30
Purchase #7	$108.85	13.767%	$123.8354	$123.84	$123.85	$123.80
7 purchase totals =	$1,035.66		$1,116.3544	$1,116.35	$1,116.35	$1,116.30