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	$206.96	6.359%	$220.1206	$220.12	$220.10	$220.10
Purchase #2	$174.77	9.830%	$191.9499	$191.95	$191.95	$191.90
Purchase #3	$192.59	7.612%	$207.25	$207.25	$207.25	$207.30
Purchase #4	$233.92	8.356%	$253.4664	$253.47	$253.45	$253.50
Purchase #5	$39.84	9.349%	$43.5646	$43.56	$43.55	$43.60
Purchase #6	$39.28	8.529%	$42.6302	$42.63	$42.65	$42.60
Purchase #7	$55.87	3.600%	$57.8813	$57.88	$57.90	$57.90
7 purchase totals =	$943.23		$1,016.8630	$1,016.86	$1,016.85	$1,016.90