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	$167.54	6.772%	$178.8858	$178.89	$178.90	$178.90
Purchase #2	$150.43	3.132%	$155.1415	$155.14	$155.15	$155.10
Purchase #3	$100.65	5.521%	$106.2069	$106.21	$106.20	$106.20
Purchase #4	$150.41	11.351%	$167.483	$167.48	$167.50	$167.50
Purchase #5	$193.39	3.473%	$200.1064	$200.11	$200.10	$200.10
Purchase #6	$86.72	10.869%	$96.1456	$96.15	$96.15	$96.10
Purchase #7	$102.88	9.229%	$112.3748	$112.37	$112.35	$112.40
7 purchase totals =	$952.02		$1,016.3440	$1,016.35	$1,016.35	$1,016.30