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	$171.86	8.133%	$185.8374	$185.84	$185.85	$185.80
Purchase #2	$181.32	10.184%	$199.7856	$199.79	$199.80	$199.80
Purchase #3	$205.27	11.241%	$228.3444	$228.34	$228.35	$228.30
Purchase #4	$80.61	12.136%	$90.3928	$90.39	$90.40	$90.40
Purchase #5	$78.58	5.589%	$82.9718	$82.97	$82.95	$83.00
Purchase #6	$87.65	9.675%	$96.1301	$96.13	$96.15	$96.10
Purchase #7	$196.44	5.520%	$207.2835	$207.28	$207.30	$207.30
7 purchase totals =	$1,001.73		$1,090.7456	$1,090.74	$1,090.80	$1,090.70