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	$70.88	10.810%	$78.5421	$78.54	$78.55	$78.50
Purchase #2	$118.58	7.302%	$127.2387	$127.24	$127.25	$127.20
Purchase #3	$82.69	7.504%	$88.8951	$88.90	$88.90	$88.90
Purchase #4	$73.58	12.627%	$82.8709	$82.87	$82.85	$82.90
Purchase #5	$137.29	13.312%	$155.566	$155.57	$155.55	$155.60
Purchase #6	$203.80	7.549%	$219.1849	$219.18	$219.20	$219.20
Purchase #7	$234.39	6.206%	$248.9362	$248.94	$248.95	$248.90
7 purchase totals =	$921.21		$1,001.2339	$1,001.24	$1,001.25	$1,001.20