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	$105.89	4.270%	$110.4115	$110.41	$110.40	$110.40
Purchase #2	$49.56	8.288%	$53.6675	$53.67	$53.65	$53.70
Purchase #3	$187.63	6.419%	$199.674	$199.67	$199.65	$199.70
Purchase #4	$29.56	13.404%	$33.5222	$33.52	$33.50	$33.50
Purchase #5	$105.93	7.623%	$114.005	$114.01	$114.00	$114.00
Purchase #6	$42.68	6.435%	$45.4265	$45.43	$45.45	$45.40
Purchase #7	$233.77	11.187%	$259.9218	$259.92	$259.90	$259.90
7 purchase totals =	$755.02		$816.6285	$816.63	$816.55	$816.60