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	$130.90	8.707%	$142.2975	$142.30	$142.30	$142.30
Purchase #2	$14.38	13.399%	$16.3068	$16.31	$16.30	$16.30
Purchase #3	$193.25	8.397%	$209.4772	$209.48	$209.50	$209.50
Purchase #4	$246.29	6.233%	$261.6413	$261.64	$261.65	$261.60
Purchase #5	$146.90	5.645%	$155.1925	$155.19	$155.20	$155.20
Purchase #6	$163.56	9.172%	$178.5617	$178.56	$178.55	$178.60
Purchase #7	$109.55	12.645%	$123.4026	$123.40	$123.40	$123.40
7 purchase totals =	$1,004.83		$1,086.8796	$1,086.88	$1,086.90	$1,086.90