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	$198.96	9.251%	$217.3658	$217.37	$217.35	$217.40
Purchase #2	$82.37	9.787%	$90.4316	$90.43	$90.45	$90.40
Purchase #3	$53.78	11.337%	$59.877	$59.88	$59.90	$59.90
Purchase #4	$132.47	7.237%	$142.0569	$142.06	$142.05	$142.10
Purchase #5	$244.91	13.721%	$278.5141	$278.51	$278.50	$278.50
Purchase #6	$197.46	12.308%	$221.7634	$221.76	$221.75	$221.80
Purchase #7	$140.51	8.755%	$152.8117	$152.81	$152.80	$152.80
7 purchase totals =	$1,050.46		$1,162.8205	$1,162.82	$1,162.80	$1,162.90