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	$188.55	5.750%	$199.3916	$199.39	$199.40	$199.40
Purchase #2	$147.77	13.230%	$167.32	$167.32	$167.30	$167.30
Purchase #3	$120.69	9.189%	$131.7802	$131.78	$131.80	$131.80
Purchase #4	$163.70	13.154%	$185.2331	$185.23	$185.25	$185.20
Purchase #5	$246.85	3.243%	$254.8553	$254.86	$254.85	$254.90
Purchase #6	$183.98	7.242%	$197.3038	$197.30	$197.30	$197.30
Purchase #7	$72.38	9.870%	$79.5239	$79.52	$79.50	$79.50
7 purchase totals =	$1,123.92		$1,215.4079	$1,215.40	$1,215.40	$1,215.40