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	$109.55	13.526%	$124.3677	$124.37	$124.35	$124.40
Purchase #2	$129.48	7.744%	$139.5069	$139.51	$139.50	$139.50
Purchase #3	$201.41	13.863%	$229.3315	$229.33	$229.35	$229.30
Purchase #4	$30.80	5.405%	$32.4647	$32.46	$32.45	$32.50
Purchase #5	$116.61	9.729%	$127.955	$127.96	$127.95	$128.00
Purchase #6	$181.96	6.387%	$193.5818	$193.58	$193.60	$193.60
Purchase #7	$152.57	13.524%	$173.2036	$173.20	$173.20	$173.20
7 purchase totals =	$922.38		$1,020.4112	$1,020.41	$1,020.40	$1,020.50