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	$110.50	11.510%	$123.2186	$123.22	$123.20	$123.20
Purchase #2	$70.46	10.760%	$78.0415	$78.04	$78.05	$78.00
Purchase #3	$240.56	9.413%	$263.2039	$263.20	$263.20	$263.20
Purchase #4	$121.92	3.858%	$126.6237	$126.62	$126.60	$126.60
Purchase #5	$202.64	6.764%	$216.3466	$216.35	$216.35	$216.30
Purchase #6	$223.56	6.518%	$238.1316	$238.13	$238.15	$238.10
Purchase #7	$151.98	10.173%	$167.4409	$167.44	$167.45	$167.40
7 purchase totals =	$1,121.62		$1,213.0068	$1,213.00	$1,213.00	$1,212.80