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	$53.95	9.801%	$59.2376	$59.24	$59.25	$59.20
Purchase #2	$106.69	5.431%	$112.4843	$112.48	$112.50	$112.50
Purchase #3	$35.65	10.123%	$39.2588	$39.26	$39.25	$39.30
Purchase #4	$211.94	8.651%	$230.2749	$230.27	$230.25	$230.30
Purchase #5	$182.69	6.349%	$194.289	$194.29	$194.30	$194.30
Purchase #6	$196.87	9.225%	$215.0313	$215.03	$215.05	$215.00
Purchase #7	$42.96	9.257%	$46.9368	$46.94	$46.95	$46.90
7 purchase totals =	$830.75		$897.5127	$897.51	$897.55	$897.50