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	$176.77	4.330%	$184.4241	$184.42	$184.40	$184.40
Purchase #2	$112.28	3.140%	$115.8056	$115.81	$115.80	$115.80
Purchase #3	$209.33	7.206%	$224.4143	$224.41	$224.40	$224.40
Purchase #4	$191.60	9.517%	$209.8346	$209.83	$209.85	$209.80
Purchase #5	$101.46	9.696%	$111.2976	$111.30	$111.30	$111.30
Purchase #6	$115.75	9.333%	$126.5529	$126.55	$126.55	$126.60
Purchase #7	$223.81	9.127%	$244.2371	$244.24	$244.25	$244.20
7 purchase totals =	$1,131.00		$1,216.5662	$1,216.56	$1,216.55	$1,216.50