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	$183.58	4.107%	$191.1196	$191.12	$191.10	$191.10
Purchase #2	$164.62	3.329%	$170.1002	$170.10	$170.10	$170.10
Purchase #3	$31.93	13.706%	$36.3063	$36.31	$36.30	$36.30
Purchase #4	$73.68	11.379%	$82.064	$82.06	$82.05	$82.10
Purchase #5	$137.41	5.754%	$145.3166	$145.32	$145.30	$145.30
Purchase #6	$131.92	5.210%	$138.793	$138.79	$138.80	$138.80
Purchase #7	$84.29	6.607%	$89.859	$89.86	$89.85	$89.90
7 purchase totals =	$807.43		$853.5587	$853.56	$853.50	$853.60