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	$174.45	5.801%	$184.5698	$184.57	$184.55	$184.60
Purchase #2	$104.52	9.335%	$114.2769	$114.28	$114.30	$114.30
Purchase #3	$198.86	10.524%	$219.788	$219.79	$219.80	$219.80
Purchase #4	$98.79	4.537%	$103.2721	$103.27	$103.25	$103.30
Purchase #5	$136.97	6.114%	$145.3443	$145.34	$145.35	$145.30
Purchase #6	$79.57	11.192%	$88.4755	$88.48	$88.50	$88.50
Purchase #7	$140.83	8.139%	$152.2922	$152.29	$152.30	$152.30
7 purchase totals =	$933.99		$1,008.0188	$1,008.02	$1,008.05	$1,008.10