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	$50.89	3.832%	$52.8401	$52.84	$52.85	$52.80
Purchase #2	$216.33	8.784%	$235.3324	$235.33	$235.35	$235.30
Purchase #3	$73.50	11.695%	$82.0958	$82.10	$82.10	$82.10
Purchase #4	$168.27	10.814%	$186.4667	$186.47	$186.45	$186.50
Purchase #5	$206.74	3.172%	$213.2978	$213.30	$213.30	$213.30
Purchase #6	$196.88	12.178%	$220.856	$220.86	$220.85	$220.90
Purchase #7	$50.79	10.170%	$55.9553	$55.96	$55.95	$56.00
7 purchase totals =	$963.40		$1,046.8441	$1,046.86	$1,046.85	$1,046.90