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	$166.66	3.366%	$172.2698	$172.27	$172.25	$172.30
Purchase #2	$90.44	9.442%	$98.9793	$98.98	$99.00	$99.00
Purchase #3	$160.31	8.840%	$174.4814	$174.48	$174.50	$174.50
Purchase #4	$30.99	9.774%	$34.019	$34.02	$34.00	$34.00
Purchase #5	$247.76	13.469%	$281.1308	$281.13	$281.15	$281.10
Purchase #6	$151.27	13.659%	$171.932	$171.93	$171.95	$171.90
Purchase #7	$164.74	3.587%	$170.6492	$170.65	$170.65	$170.60
7 purchase totals =	$1,012.17		$1,103.4615	$1,103.46	$1,103.50	$1,103.40