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	$144.91	4.472%	$151.3904	$151.39	$151.40	$151.40
Purchase #2	$114.96	4.322%	$119.9286	$119.93	$119.95	$119.90
Purchase #3	$101.39	13.565%	$115.1436	$115.14	$115.15	$115.10
Purchase #4	$175.97	3.766%	$182.597	$182.60	$182.60	$182.60
Purchase #5	$25.78	6.864%	$27.5495	$27.55	$27.55	$27.50
Purchase #6	$73.41	11.735%	$82.0247	$82.02	$82.00	$82.00
Purchase #7	$234.45	5.605%	$247.5909	$247.59	$247.60	$247.60
7 purchase totals =	$870.87		$926.2247	$926.22	$926.25	$926.10