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	$52.62	4.739%	$55.1137	$55.11	$55.10	$55.10
Purchase #2	$155.33	6.454%	$165.355	$165.36	$165.35	$165.40
Purchase #3	$141.33	9.386%	$154.5952	$154.60	$154.60	$154.60
Purchase #4	$27.61	4.295%	$28.7958	$28.80	$28.80	$28.80
Purchase #5	$227.34	8.458%	$246.5684	$246.57	$246.55	$246.60
Purchase #6	$185.93	5.705%	$196.5373	$196.54	$196.55	$196.50
Purchase #7	$68.88	12.629%	$77.5789	$77.58	$77.60	$77.60
7 purchase totals =	$859.04		$924.5443	$924.56	$924.55	$924.60