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	$108.52	10.173%	$119.5597	$119.56	$119.55	$119.60
Purchase #2	$178.63	3.696%	$185.2322	$185.23	$185.25	$185.20
Purchase #3	$172.88	6.535%	$184.1777	$184.18	$184.20	$184.20
Purchase #4	$77.40	10.773%	$85.7383	$85.74	$85.75	$85.70
Purchase #5	$223.30	11.159%	$248.218	$248.22	$248.20	$248.20
Purchase #6	$244.64	8.872%	$266.3445	$266.34	$266.35	$266.30
Purchase #7	$45.85	10.307%	$50.5758	$50.58	$50.60	$50.60
7 purchase totals =	$1,051.22		$1,139.8462	$1,139.85	$1,139.90	$1,139.80