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	$187.44	6.129%	$198.9282	$198.93	$198.95	$198.90
Purchase #2	$224.47	7.324%	$240.9102	$240.91	$240.90	$240.90
Purchase #3	$35.84	4.423%	$37.4252	$37.43	$37.45	$37.40
Purchase #4	$240.50	7.870%	$259.4274	$259.43	$259.45	$259.40
Purchase #5	$193.91	7.457%	$208.3699	$208.37	$208.35	$208.40
Purchase #6	$142.63	3.286%	$147.3168	$147.32	$147.30	$147.30
Purchase #7	$85.29	4.805%	$89.3882	$89.39	$89.40	$89.40
7 purchase totals =	$1,110.08		$1,181.7659	$1,181.78	$1,181.80	$1,181.70