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	$73.46	13.764%	$83.571	$83.57	$83.55	$83.60
Purchase #2	$196.87	9.855%	$216.2715	$216.27	$216.25	$216.30
Purchase #3	$237.61	7.798%	$256.1388	$256.14	$256.15	$256.10
Purchase #4	$46.99	13.224%	$53.204	$53.20	$53.20	$53.20
Purchase #5	$196.38	6.746%	$209.6278	$209.63	$209.65	$209.60
Purchase #6	$150.34	8.146%	$162.5867	$162.59	$162.60	$162.60
Purchase #7	$219.44	11.132%	$243.8681	$243.87	$243.85	$243.90
7 purchase totals =	$1,121.09		$1,225.2679	$1,225.27	$1,225.25	$1,225.30