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	$196.34	9.628%	$215.2436	$215.24	$215.25	$215.20
Purchase #2	$168.99	10.337%	$186.4585	$186.46	$186.45	$186.50
Purchase #3	$247.90	11.552%	$276.5374	$276.54	$276.55	$276.50
Purchase #4	$43.89	3.257%	$45.3195	$45.32	$45.30	$45.30
Purchase #5	$114.74	7.202%	$123.0036	$123.00	$123.00	$123.00
Purchase #6	$50.54	12.333%	$56.7731	$56.77	$56.75	$56.80
Purchase #7	$196.25	6.192%	$208.4018	$208.40	$208.40	$208.40
7 purchase totals =	$1,018.65		$1,111.7375	$1,111.73	$1,111.70	$1,111.70