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	$17.39	10.605%	$19.2342	$19.23	$19.25	$19.20
Purchase #2	$35.61	8.814%	$38.7487	$38.75	$38.75	$38.70
Purchase #3	$175.34	6.581%	$186.8791	$186.88	$186.90	$186.90
Purchase #4	$10.42	10.138%	$11.4764	$11.48	$11.50	$11.50
Purchase #5	$56.31	9.339%	$61.5688	$61.57	$61.55	$61.60
Purchase #6	$190.45	3.156%	$196.4606	$196.46	$196.45	$196.50
Purchase #7	$239.87	11.813%	$268.2058	$268.21	$268.20	$268.20
7 purchase totals =	$725.39		$782.5736	$782.58	$782.60	$782.60