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	$228.61	9.617%	$250.5954	$250.60	$250.60	$250.60
Purchase #2	$39.59	4.719%	$41.4583	$41.46	$41.45	$41.50
Purchase #3	$245.54	13.578%	$278.8794	$278.88	$278.90	$278.90
Purchase #4	$87.64	4.527%	$91.6075	$91.61	$91.60	$91.60
Purchase #5	$201.47	13.640%	$228.9505	$228.95	$228.95	$229.00
Purchase #6	$49.76	9.294%	$54.3847	$54.38	$54.40	$54.40
Purchase #7	$185.74	5.766%	$196.4498	$196.45	$196.45	$196.40
7 purchase totals =	$1,038.35		$1,142.3256	$1,142.33	$1,142.35	$1,142.40