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	$170.33	4.269%	$177.6014	$177.60	$177.60	$177.60
Purchase #2	$163.88	6.246%	$174.1159	$174.12	$174.10	$174.10
Purchase #3	$53.72	3.813%	$55.7683	$55.77	$55.75	$55.80
Purchase #4	$33.79	11.751%	$37.7607	$37.76	$37.75	$37.80
Purchase #5	$69.33	3.123%	$71.4952	$71.50	$71.50	$71.50
Purchase #6	$198.58	9.206%	$216.8613	$216.86	$216.85	$216.90
Purchase #7	$111.81	6.740%	$119.346	$119.35	$119.35	$119.30
7 purchase totals =	$801.44		$852.9488	$852.96	$852.90	$853.00