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	$236.71	11.755%	$264.5353	$264.54	$264.55	$264.50
Purchase #2	$21.68	9.625%	$23.7667	$23.77	$23.75	$23.80
Purchase #3	$229.61	4.702%	$240.4063	$240.41	$240.40	$240.40
Purchase #4	$105.33	7.343%	$113.0644	$113.06	$113.05	$113.10
Purchase #5	$246.49	13.841%	$280.6067	$280.61	$280.60	$280.60
Purchase #6	$112.58	3.563%	$116.5912	$116.59	$116.60	$116.60
Purchase #7	$249.89	10.152%	$275.2588	$275.26	$275.25	$275.30
7 purchase totals =	$1,202.29		$1,314.2294	$1,314.24	$1,314.20	$1,314.30