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	$53.32	11.274%	$59.3313	$59.33	$59.35	$59.30
Purchase #2	$129.93	9.394%	$142.1356	$142.14	$142.15	$142.10
Purchase #3	$150.59	13.236%	$170.5221	$170.52	$170.50	$170.50
Purchase #4	$174.65	10.242%	$192.5377	$192.54	$192.55	$192.50
Purchase #5	$185.76	10.654%	$205.5509	$205.55	$205.55	$205.60
Purchase #6	$5.58	5.396%	$5.8811	$5.88	$5.90	$5.90
Purchase #7	$227.98	9.756%	$250.2217	$250.22	$250.20	$250.20
7 purchase totals =	$927.81		$1,026.1804	$1,026.18	$1,026.20	$1,026.10