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	$186.31	5.612%	$196.7657	$196.77	$196.75	$196.80
Purchase #2	$7.53	3.550%	$7.7973	$7.80	$7.80	$7.80
Purchase #3	$13.60	9.228%	$14.855	$14.86	$14.85	$14.90
Purchase #4	$176.34	5.274%	$185.6402	$185.64	$185.65	$185.60
Purchase #5	$88.62	3.641%	$91.8467	$91.85	$91.85	$91.80
Purchase #6	$168.66	7.327%	$181.0177	$181.02	$181.00	$181.00
Purchase #7	$199.43	11.481%	$222.3266	$222.33	$222.35	$222.30
7 purchase totals =	$840.49		$900.2492	$900.27	$900.25	$900.20