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	$35.69	6.244%	$37.9185	$37.92	$37.90	$37.90
Purchase #2	$112.39	4.612%	$117.5734	$117.57	$117.55	$117.60
Purchase #3	$174.97	6.473%	$186.2958	$186.30	$186.30	$186.30
Purchase #4	$139.91	8.872%	$152.3228	$152.32	$152.30	$152.30
Purchase #5	$117.68	6.584%	$125.4281	$125.43	$125.45	$125.40
Purchase #6	$237.39	11.238%	$264.0679	$264.07	$264.05	$264.10
Purchase #7	$208.66	9.123%	$227.6961	$227.70	$227.70	$227.70
7 purchase totals =	$1,026.69		$1,111.3026	$1,111.31	$1,111.25	$1,111.30