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	$245.71	8.612%	$266.8705	$266.87	$266.85	$266.90
Purchase #2	$228.78	3.252%	$236.2199	$236.22	$236.20	$236.20
Purchase #3	$160.93	11.564%	$179.5399	$179.54	$179.55	$179.50
Purchase #4	$112.60	13.146%	$127.4024	$127.40	$127.40	$127.40
Purchase #5	$17.89	7.361%	$19.2069	$19.21	$19.20	$19.20
Purchase #6	$68.32	6.394%	$72.6884	$72.69	$72.70	$72.70
Purchase #7	$174.88	12.623%	$196.9551	$196.96	$196.95	$197.00
7 purchase totals =	$1,009.11		$1,098.8831	$1,098.89	$1,098.85	$1,098.90