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	$177.28	4.630%	$185.4881	$185.49	$185.50	$185.50
Purchase #2	$119.70	7.693%	$128.9085	$128.91	$128.90	$128.90
Purchase #3	$221.62	4.705%	$232.0472	$232.05	$232.05	$232.00
Purchase #4	$95.63	4.504%	$99.9372	$99.94	$99.95	$99.90
Purchase #5	$119.38	9.862%	$131.1533	$131.15	$131.15	$131.20
Purchase #6	$215.83	9.413%	$236.1461	$236.15	$236.15	$236.10
Purchase #7	$106.44	7.213%	$114.1175	$114.12	$114.10	$114.10
7 purchase totals =	$1,055.88		$1,127.7979	$1,127.81	$1,127.80	$1,127.70