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	$201.75	3.872%	$209.5618	$209.56	$209.55	$209.60
Purchase #2	$179.58	9.446%	$196.5431	$196.54	$196.55	$196.50
Purchase #3	$200.31	13.171%	$226.6928	$226.69	$226.70	$226.70
Purchase #4	$53.73	3.480%	$55.5998	$55.60	$55.60	$55.60
Purchase #5	$106.31	10.454%	$117.4236	$117.42	$117.40	$117.40
Purchase #6	$130.55	11.286%	$145.2839	$145.28	$145.30	$145.30
Purchase #7	$126.92	7.409%	$136.3235	$136.32	$136.30	$136.30
7 purchase totals =	$999.15		$1,087.4285	$1,087.41	$1,087.40	$1,087.40