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	$208.25	7.518%	$223.9062	$223.91	$223.90	$223.90
Purchase #2	$82.59	5.220%	$86.9012	$86.90	$86.90	$86.90
Purchase #3	$72.64	3.508%	$75.1882	$75.19	$75.20	$75.20
Purchase #4	$180.69	4.729%	$189.2348	$189.23	$189.25	$189.20
Purchase #5	$96.96	12.651%	$109.2264	$109.23	$109.25	$109.20
Purchase #6	$80.31	3.818%	$83.3762	$83.38	$83.40	$83.40
Purchase #7	$212.83	13.303%	$241.1428	$241.14	$241.15	$241.10
7 purchase totals =	$934.27		$1,008.9758	$1,008.98	$1,009.05	$1,008.90