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	$236.73	11.493%	$263.9374	$263.94	$263.95	$263.90
Purchase #2	$120.81	11.194%	$134.3335	$134.33	$134.35	$134.30
Purchase #3	$151.84	11.870%	$169.8634	$169.86	$169.85	$169.90
Purchase #4	$86.33	11.379%	$96.1535	$96.15	$96.15	$96.20
Purchase #5	$116.90	12.499%	$131.5113	$131.51	$131.50	$131.50
Purchase #6	$170.54	10.553%	$188.5371	$188.54	$188.55	$188.50
Purchase #7	$156.96	6.617%	$167.346	$167.35	$167.35	$167.30
7 purchase totals =	$1,040.11		$1,151.6822	$1,151.68	$1,151.70	$1,151.60