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	$195.61	6.351%	$208.0332	$208.03	$208.05	$208.00
Purchase #2	$42.92	3.270%	$44.3235	$44.32	$44.30	$44.30
Purchase #3	$196.85	11.742%	$219.9641	$219.96	$219.95	$220.00
Purchase #4	$99.39	6.171%	$105.5234	$105.52	$105.50	$105.50
Purchase #5	$44.67	4.767%	$46.7994	$46.80	$46.80	$46.80
Purchase #6	$50.87	4.445%	$53.1312	$53.13	$53.15	$53.10
Purchase #7	$200.54	7.482%	$215.5444	$215.54	$215.55	$215.50
7 purchase totals =	$830.85		$893.3192	$893.30	$893.30	$893.20