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	$196.68	10.608%	$217.5438	$217.54	$217.55	$217.50
Purchase #2	$126.72	11.767%	$141.6311	$141.63	$141.65	$141.60
Purchase #3	$204.41	13.696%	$232.406	$232.41	$232.40	$232.40
Purchase #4	$237.27	5.385%	$250.047	$250.05	$250.05	$250.00
Purchase #5	$131.50	7.267%	$141.0561	$141.06	$141.05	$141.10
Purchase #6	$114.61	7.751%	$123.4934	$123.49	$123.50	$123.50
Purchase #7	$95.36	9.155%	$104.0902	$104.09	$104.10	$104.10
7 purchase totals =	$1,106.55		$1,210.2676	$1,210.27	$1,210.30	$1,210.20