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	$90.96	7.293%	$97.5937	$97.59	$97.60	$97.60
Purchase #2	$44.57	11.145%	$49.5373	$49.54	$49.55	$49.50
Purchase #3	$51.82	6.127%	$54.995	$55.00	$55.00	$55.00
Purchase #4	$33.63	10.419%	$37.1339	$37.13	$37.15	$37.10
Purchase #5	$47.48	11.774%	$53.0703	$53.07	$53.05	$53.10
Purchase #6	$97.48	12.764%	$109.9223	$109.92	$109.90	$109.90
Purchase #7	$77.32	6.474%	$82.3257	$82.33	$82.35	$82.30
7 purchase totals =	$443.26		$484.5782	$484.58	$484.60	$484.50