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	$87.83	12.656%	$98.9458	$98.95	$98.95	$98.90
Purchase #2	$172.65	4.157%	$179.8271	$179.83	$179.85	$179.80
Purchase #3	$198.63	5.474%	$209.503	$209.50	$209.50	$209.50
Purchase #4	$171.74	4.580%	$179.6057	$179.61	$179.60	$179.60
Purchase #5	$101.67	10.431%	$112.2752	$112.28	$112.30	$112.30
Purchase #6	$64.70	10.452%	$71.4624	$71.46	$71.45	$71.50
Purchase #7	$242.43	7.722%	$261.1504	$261.15	$261.15	$261.20
7 purchase totals =	$1,039.65		$1,112.7696	$1,112.78	$1,112.80	$1,112.80