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	$34.41	3.570%	$35.6384	$35.64	$35.65	$35.60
Purchase #2	$237.56	5.812%	$251.367	$251.37	$251.35	$251.40
Purchase #3	$75.70	11.375%	$84.3109	$84.31	$84.30	$84.30
Purchase #4	$70.78	13.721%	$80.4917	$80.49	$80.50	$80.50
Purchase #5	$181.66	10.563%	$200.8487	$200.85	$200.85	$200.80
Purchase #6	$245.82	12.171%	$275.7388	$275.74	$275.75	$275.70
Purchase #7	$239.63	11.776%	$267.8488	$267.85	$267.85	$267.80
7 purchase totals =	$1,085.56		$1,196.2443	$1,196.25	$1,196.25	$1,196.10