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	$82.82	7.793%	$89.2742	$89.27	$89.25	$89.30
Purchase #2	$89.29	3.738%	$92.6277	$92.63	$92.65	$92.60
Purchase #3	$105.77	5.829%	$111.9353	$111.94	$111.95	$111.90
Purchase #4	$142.74	5.361%	$150.3923	$150.39	$150.40	$150.40
Purchase #5	$243.89	11.486%	$271.9032	$271.90	$271.90	$271.90
Purchase #6	$205.95	11.684%	$230.0132	$230.01	$230.00	$230.00
Purchase #7	$90.66	7.354%	$97.3271	$97.33	$97.35	$97.30
7 purchase totals =	$961.12		$1,043.4730	$1,043.47	$1,043.50	$1,043.40