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	$97.81	4.264%	$101.9806	$101.98	$102.00	$102.00
Purchase #2	$179.29	4.837%	$187.9623	$187.96	$187.95	$188.00
Purchase #3	$213.33	4.257%	$222.4115	$222.41	$222.40	$222.40
Purchase #4	$213.36	12.755%	$240.5741	$240.57	$240.55	$240.60
Purchase #5	$38.78	7.565%	$41.7137	$41.71	$41.70	$41.70
Purchase #6	$196.84	3.705%	$204.1329	$204.13	$204.15	$204.10
Purchase #7	$76.78	12.543%	$86.4105	$86.41	$86.40	$86.40
7 purchase totals =	$1,016.19		$1,085.1856	$1,085.17	$1,085.15	$1,085.20