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	$182.92	12.159%	$205.1612	$205.16	$205.15	$205.20
Purchase #2	$177.77	6.724%	$189.7233	$189.72	$189.70	$189.70
Purchase #3	$44.86	3.667%	$46.505	$46.51	$46.50	$46.50
Purchase #4	$91.77	12.368%	$103.1201	$103.12	$103.10	$103.10
Purchase #5	$154.82	10.797%	$171.5359	$171.54	$171.55	$171.50
Purchase #6	$80.33	12.834%	$90.6396	$90.64	$90.65	$90.60
Purchase #7	$185.95	5.310%	$195.8239	$195.82	$195.80	$195.80
7 purchase totals =	$918.42		$1,002.5090	$1,002.51	$1,002.45	$1,002.40