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	$201.55	11.855%	$225.4438	$225.44	$225.45	$225.40
Purchase #2	$191.27	9.405%	$209.2589	$209.26	$209.25	$209.30
Purchase #3	$84.42	7.517%	$90.7659	$90.77	$90.75	$90.80
Purchase #4	$241.31	11.597%	$269.2947	$269.29	$269.30	$269.30
Purchase #5	$117.55	10.113%	$129.4378	$129.44	$129.45	$129.40
Purchase #6	$36.47	6.191%	$38.7279	$38.73	$38.75	$38.70
Purchase #7	$50.81	11.351%	$56.5774	$56.58	$56.60	$56.60
7 purchase totals =	$923.38		$1,019.5064	$1,019.51	$1,019.55	$1,019.50