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	$40.97	6.318%	$43.5585	$43.56	$43.55	$43.60
Purchase #2	$233.92	6.135%	$248.271	$248.27	$248.25	$248.30
Purchase #3	$174.73	12.444%	$196.4734	$196.47	$196.45	$196.50
Purchase #4	$28.37	13.861%	$32.3024	$32.30	$32.30	$32.30
Purchase #5	$90.53	6.638%	$96.5394	$96.54	$96.55	$96.50
Purchase #6	$232.38	12.203%	$260.7373	$260.74	$260.75	$260.70
Purchase #7	$155.68	13.300%	$176.3854	$176.39	$176.40	$176.40
7 purchase totals =	$956.58		$1,054.2674	$1,054.27	$1,054.25	$1,054.30