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	$244.40	8.270%	$264.6119	$264.61	$264.60	$264.60
Purchase #2	$79.27	4.631%	$82.941	$82.94	$82.95	$82.90
Purchase #3	$57.42	9.566%	$62.9128	$62.91	$62.90	$62.90
Purchase #4	$167.91	3.230%	$173.3335	$173.33	$173.35	$173.30
Purchase #5	$121.93	6.704%	$130.1042	$130.10	$130.10	$130.10
Purchase #6	$187.72	7.342%	$201.5024	$201.50	$201.50	$201.50
Purchase #7	$98.85	8.766%	$107.5152	$107.52	$107.50	$107.50
7 purchase totals =	$957.50		$1,022.9210	$1,022.91	$1,022.90	$1,022.80