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	$206.37	6.374%	$219.524	$219.52	$219.50	$219.50
Purchase #2	$245.79	11.404%	$273.8199	$273.82	$273.80	$273.80
Purchase #3	$187.41	9.426%	$205.0753	$205.08	$205.10	$205.10
Purchase #4	$233.53	13.864%	$265.9066	$265.91	$265.90	$265.90
Purchase #5	$125.61	13.754%	$142.8864	$142.89	$142.90	$142.90
Purchase #6	$69.97	3.362%	$72.3224	$72.32	$72.30	$72.30
Purchase #7	$136.32	7.445%	$146.469	$146.47	$146.45	$146.50
7 purchase totals =	$1,205.00		$1,326.0036	$1,326.01	$1,325.95	$1,326.00