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	$196.52	3.435%	$203.2705	$203.27	$203.25	$203.30
Purchase #2	$45.49	10.601%	$50.3124	$50.31	$50.30	$50.30
Purchase #3	$178.96	5.298%	$188.4413	$188.44	$188.45	$188.40
Purchase #4	$40.85	5.383%	$43.049	$43.05	$43.05	$43.00
Purchase #5	$161.88	12.751%	$182.5213	$182.52	$182.50	$182.50
Purchase #6	$164.28	12.777%	$185.2701	$185.27	$185.25	$185.30
Purchase #7	$212.40	8.704%	$230.8873	$230.89	$230.90	$230.90
7 purchase totals =	$1,000.38		$1,083.7519	$1,083.75	$1,083.70	$1,083.70