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	$198.43	7.505%	$213.3222	$213.32	$213.30	$213.30
Purchase #2	$82.44	8.134%	$89.1457	$89.15	$89.15	$89.10
Purchase #3	$197.32	4.329%	$205.862	$205.86	$205.85	$205.90
Purchase #4	$154.94	9.445%	$169.5741	$169.57	$169.55	$169.60
Purchase #5	$212.99	11.718%	$237.9482	$237.95	$237.95	$237.90
Purchase #6	$166.56	12.837%	$187.9413	$187.94	$187.95	$187.90
Purchase #7	$103.27	8.561%	$112.1109	$112.11	$112.10	$112.10
7 purchase totals =	$1,115.95		$1,215.9044	$1,215.90	$1,215.85	$1,215.80