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	$114.45	13.488%	$129.887	$129.89	$129.90	$129.90
Purchase #2	$199.49	12.191%	$223.8098	$223.81	$223.80	$223.80
Purchase #3	$31.80	4.573%	$33.2542	$33.25	$33.25	$33.30
Purchase #4	$107.36	6.489%	$114.3266	$114.33	$114.35	$114.30
Purchase #5	$186.66	4.440%	$194.9477	$194.95	$194.95	$194.90
Purchase #6	$169.36	9.696%	$185.7811	$185.78	$185.80	$185.80
Purchase #7	$168.78	7.577%	$181.5685	$181.57	$181.55	$181.60
7 purchase totals =	$977.90		$1,063.5749	$1,063.58	$1,063.60	$1,063.60