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	$138.49	13.407%	$157.0574	$157.06	$157.05	$157.10
Purchase #2	$70.53	3.418%	$72.9407	$72.94	$72.95	$72.90
Purchase #3	$181.72	9.373%	$198.7526	$198.75	$198.75	$198.80
Purchase #4	$85.86	4.599%	$89.8087	$89.81	$89.80	$89.80
Purchase #5	$157.78	7.818%	$170.1152	$170.12	$170.10	$170.10
Purchase #6	$105.83	11.771%	$118.2872	$118.29	$118.30	$118.30
Purchase #7	$210.79	5.833%	$223.0854	$223.09	$223.10	$223.10
7 purchase totals =	$951.00		$1,030.0472	$1,030.06	$1,030.05	$1,030.10