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	$37.27	11.468%	$41.5441	$41.54	$41.55	$41.50
Purchase #2	$238.51	12.558%	$268.4621	$268.46	$268.45	$268.50
Purchase #3	$147.62	12.436%	$165.978	$165.98	$166.00	$166.00
Purchase #4	$62.32	8.836%	$67.8266	$67.83	$67.85	$67.80
Purchase #5	$228.92	3.211%	$236.2706	$236.27	$236.25	$236.30
Purchase #6	$179.53	8.541%	$194.8637	$194.86	$194.85	$194.90
Purchase #7	$187.40	9.620%	$205.4279	$205.43	$205.45	$205.40
7 purchase totals =	$1,081.57		$1,180.3730	$1,180.37	$1,180.40	$1,180.40