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	$184.88	6.481%	$196.8621	$196.86	$196.85	$196.90
Purchase #2	$83.30	7.832%	$89.8241	$89.82	$89.80	$89.80
Purchase #3	$60.46	11.264%	$67.2702	$67.27	$67.25	$67.30
Purchase #4	$195.87	9.217%	$213.9233	$213.92	$213.90	$213.90
Purchase #5	$243.95	13.230%	$276.2246	$276.22	$276.20	$276.20
Purchase #6	$148.78	10.686%	$164.6786	$164.68	$164.70	$164.70
Purchase #7	$205.66	7.286%	$220.6444	$220.64	$220.65	$220.60
7 purchase totals =	$1,122.90		$1,229.4273	$1,229.41	$1,229.35	$1,229.40