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	$93.58	5.317%	$98.5556	$98.56	$98.55	$98.60
Purchase #2	$221.73	8.786%	$241.2112	$241.21	$241.20	$241.20
Purchase #3	$105.90	3.257%	$109.3492	$109.35	$109.35	$109.30
Purchase #4	$59.52	13.860%	$67.7695	$67.77	$67.75	$67.80
Purchase #5	$223.51	6.735%	$238.5634	$238.56	$238.55	$238.60
Purchase #6	$110.45	8.164%	$119.4671	$119.47	$119.45	$119.50
Purchase #7	$56.82	4.830%	$59.5644	$59.56	$59.55	$59.60
7 purchase totals =	$871.51		$934.4804	$934.48	$934.40	$934.60