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	$127.31	7.847%	$137.3	$137.30	$137.30	$137.30
Purchase #2	$123.51	3.149%	$127.3993	$127.40	$127.40	$127.40
Purchase #3	$194.74	13.554%	$221.1351	$221.14	$221.15	$221.10
Purchase #4	$14.53	5.256%	$15.2937	$15.29	$15.30	$15.30
Purchase #5	$235.28	5.440%	$248.0792	$248.08	$248.10	$248.10
Purchase #6	$187.30	5.655%	$197.8918	$197.89	$197.90	$197.90
Purchase #7	$167.44	7.860%	$180.6008	$180.60	$180.60	$180.60
7 purchase totals =	$1,050.11		$1,127.6999	$1,127.70	$1,127.75	$1,127.70