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	$111.26	8.646%	$120.8795	$120.88	$120.90	$120.90
Purchase #2	$222.92	6.519%	$237.4522	$237.45	$237.45	$237.50
Purchase #3	$225.73	4.112%	$235.012	$235.01	$235.00	$235.00
Purchase #4	$19.41	5.862%	$20.5478	$20.55	$20.55	$20.50
Purchase #5	$211.95	11.773%	$236.9029	$236.90	$236.90	$236.90
Purchase #6	$62.58	12.612%	$70.4726	$70.47	$70.45	$70.50
Purchase #7	$99.56	4.760%	$104.2991	$104.30	$104.30	$104.30
7 purchase totals =	$953.41		$1,025.5661	$1,025.56	$1,025.55	$1,025.60