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	$145.59	3.667%	$150.9288	$150.93	$150.95	$150.90
Purchase #2	$141.46	4.383%	$147.6602	$147.66	$147.65	$147.70
Purchase #3	$250.85	4.424%	$261.9476	$261.95	$261.95	$261.90
Purchase #4	$65.86	5.749%	$69.6463	$69.65	$69.65	$69.60
Purchase #5	$79.47	6.590%	$84.7071	$84.71	$84.70	$84.70
Purchase #6	$160.82	7.123%	$172.2752	$172.28	$172.30	$172.30
Purchase #7	$241.80	5.645%	$255.4496	$255.45	$255.45	$255.40
7 purchase totals =	$1,085.85		$1,142.6148	$1,142.63	$1,142.65	$1,142.50