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	$60.60	5.845%	$64.1421	$64.14	$64.15	$64.10
Purchase #2	$69.54	4.345%	$72.5615	$72.56	$72.55	$72.60
Purchase #3	$96.60	5.818%	$102.2202	$102.22	$102.20	$102.20
Purchase #4	$225.59	3.470%	$233.418	$233.42	$233.40	$233.40
Purchase #5	$169.96	7.319%	$182.3994	$182.40	$182.40	$182.40
Purchase #6	$142.62	13.457%	$161.8124	$161.81	$161.80	$161.80
Purchase #7	$174.71	5.598%	$184.4903	$184.49	$184.50	$184.50
7 purchase totals =	$939.62		$1,001.0439	$1,001.04	$1,001.00	$1,001.00